Unfortunately one-sided and misleading, because your arguments may be correct in terms of difficulty and the thief, but the bottom line is that it only leads to relativization by ignoring many other previous arguments (see megathread) as to why BG 3 supposedly doesn't need a larger party size.
How many times have I been in a situation where I wanted to use this or that ability but didn't have it and was annoyed that I could only use a standard attack or the next turn started and the opponent repositioned...? How many items have I found and thought were cool, but I don't have a suitable party member for them. And in terms of RP, I would also have more answer options.
As has been clearly and repeatedly elaborated in the megathread, it's about the fun factor. Making a larger party smaller to have an increased challenge/difficulty is always possible. In addition, it was already foreseeable at the time that future mods would always include additional mobs, NPCs, bosses etc., as with any game, which automatically contribute to an increased level of difficulty. The other way around is not so easy without a workaround for bugs which partly lead to broken save files.
I am not criticizing your counterarguments per se. I just want to sensitize you to the fact that your POV unfortunately only allows for one unsolidary direction: namely the aforementioned relativization and thus argumentation as to why it is not needed. That's probably why Larian didn't even think about adapting vehicles and elevators, etc. in the core game to avoid major annoying bugs e. g. Underdark boat. I think the modding scene would have been happier with that alone...
