So, in BG3-EA, if you want to backstab each round, you can most times without risk. I have seen mobs move a few feet to hit me in the back and then move back in front on the same turn :P LOL. I presume most players do not use it every turn just to save time and it would get crazy boring, unless the character has the Sneak Attack feature.
Anyhow, with easy Flanking (with an ally), remove the Backstab unless the BG3 combat system is adapted fully for it (ie. therefore not saying BG3 must be like 5e).
I think players use backstab each turn to improve their %to hit but often with the jump/disengage bonus action. As you said we can move arround targets without any AOO but we have to do it step by step, which is tedious.
Totally agree with flanking. I hope they'll get rid of backstab to add flanking.
This would increase synergies between companions, this would add a lot of utility to "tank classes" and this would avoid jumping all the time to have a free advantage.