The fact that the GM has the last word doesn't mean that word is right. The world is full of bad Game Masters.
Aswell as bad players ...
And lots and lots other bad persons, and things.

What kind of an answer is that? Let's ignore bad decisions from a particular party because the other one makes bad decisions too?
"I don't think green water is healthy"
"Well yeah, but leaves are green too!"
Answer:
Everything that doesn't look and/or work the way it is supposed to be in the setting.
Yes ... this is perfectly logical and undersandable ...
Except that "is supposed to be" part.
Since your GM is the one who call how thigs "are supposed to be" ... and yet you dismiss that, since he "is not right" or "is a bad GM" ...
So ... since you said: "
This is not "my liking", this is how the setting is built."
Im not quire sure where do you take how things "are supposed to be" ...
Bcs unless i understand it incorectly, you dont use your own opinions, nor opinions of your bad GM. O_o
Nonono, wait a second. There is a way on how "things are supposed to be" when we are talking about a setting, which is all the documentation (manuals, novels etc.) that form the canon of that setting.
In the FR setting, non-magical weapons don't float mid-air in normal circumstances, where "normal"=no magic involved.
The fact that a GM choose to take parts of the
established setting and change them is a legitimate action, but also a highly criticisable one.
And, in this instance, I criticize it as a bad decision, for all the explanations provided in the other posts.
Besides, let's face it, weapons are not floating mid-air because is a "unique take of the GM on the setting"; weapons are floating mid-air for a technical shortcut, and it shows. It's this more than anything that causes the narrative dissonance and suspends the disbelief, because, unlike the beautifully crafted cinematics, it's a feature screaming
"YOU ARE IN A VIDEOGAME, THIS IS NOT REAL, WEAPONS ARE STICK ON THE BACK BECAUSE WE DIDN'T BOTHER TO PUT A PROPER ANIMATION (THAT WE HAD IN OUR PREVIOUS GAMES BTW)" in your face.
... for example if my GM would claim that in this world there are Flying rocks, that defile gravity with their very existence, but dont have any own source of power that would provide it (aka magic) ... i would not question flying sword (since there obviously are things that defile gravity and sword is comparable, or smaller items when compared to stone ... like matter, potentialy material, size, weight, etc.) ...
But if we would later find flying mountain (just an example of exaggerated breaking of the same law) ... i would probably have some questions.

Exactly, the problem is that in the FR mundane weapons don't fly on your back

Honestly mate, I may not like the excessive sarcasm you put in every single one of your posts, but I have found merits to your arguments on different occasions, even if my stance was different. Now seems to me you are just arguing for the sake of it.
You are the one who was complaining about people wanting to change the game to their liking to the detriment of your own experience (e.g. fast travel) while they could have "just ignored" those features they were complaining about. And now? Now you are defending a clearly bad feature, that doesn't make any logical sense not in-game nor in the real world and from which NO ONE would suffer if it was corrected.
Honestly Rag, without malice, name a single negative aspect if the weapons in this game were properly sheeted.
Okay, be honest Rag. Do you actually believe that when the characters stow their swords floating on their backs, that that is a literal representation of what's happening? Do you believe that the weapons are literally floating there within the reality of the game? Because I do not. What I see is the game transparently using a shortcut that many, MANY games like it have used in the past. I think it's perfectly fair for them to use it, but the game isn't even attempting to claim that it's happening in-universe. Sure, we can SEE it happening, but as you've pointed out with the map, just becaues we see something doesn't mean it's not an abstraction.
As others have pointed out, this game is taking place in the setting of Faerun, a setting that has a lot of stuff already written about it. So it is not only reasonable but logical for people coming in to assume that Larian, being the GM, will stick to the established setting until stated otherwise. Larian has made no attempt to fold the floating weapons into lore in any way. And given the fact that this is a video game, and the approach they're using for the weapons is one used in many other games over the years, the logical assumption is that what we're seeing is an abstraction. Because what reason do we have to think otherwise?
Exactly, thank you.
So the salient information here is "I don't like floating swords, teleporting badgers or pocket-dimension camps" not "my delicate sense of immersion is shattered which indicates malicious intent from the developers."
Exactly again.
"Floating weapons" are just a case study. Of course they didn't put them there because they are trying to change the setting of the FR, it's just a (bad) technical choice which should be corrected.
All this topic has became more hot of what it really should have.
The matter is simple: this game, at its current state, has some features that are really detrimental to an immersive experience, because they are breaking the disbelief of the players to be in a coherent, even if fantastical, world.
Some features are necessary for the game to function with some degree of enjoyment (minimap, fast travel etc), while others offer nothing than breaking your immersion (weapons glued to your back).