Vincke: Based on the 5th Edition because we ported all the rules to the computer game and looked at what worked and what didn’t work. There are somethings that don’t work for video games. But there is also the aspect if you’re playing tabletop, the game master and imaginations is a large part of it. There are things that are just not described in the rule set that you could do and we obviously have to make it work inside of the video game, that is something that we have to add on top of it.
The highlighted is obviously a lie though. Baldur's Gate 3 does not have a proper reaction system, and comments by Swen/Larian have heavily implied that they are still working on the reaction system to make it work better with 5e. But how can they simultaneously have had "ported [5e's reaction system] to the computer game" and yet, 1 year after EA release, 2-4 years past initial development, still have a reaction system with less functionality than tabletop that they're trying to make work more like 5e? Shouldn't they just able able to use that original build?
There are numerous other aspects of BG3 that don't make any sense if Larian truly "ported all the rules to the computer game" first. Height and Backstab Advantage, countless spells, shove checks not working properly (atheletics vs athletics/acrobatics skill check), jump+disengage bonus action, bonus action hide, darkvision, the short rest system, Prone implementing unconscious (and losing concentration), casting 2 leveled spells in a turn, surfaces, mage hand being a summon, the list goes on. And many of these are universal things, not niche "one subclass's ability" things that it'd be reasonable for Larian to implement only in later builds.
Sure, it's possible that - Larian implemented all of these exactly matching 5e (modulo bugs and misunderstanding the rules) - Larian then changed these things to their homebrew versions - For a good number of them, Larian then changed BACK to closer to RAW
But it's overwhelmingly more likely that Larian did not start with a build that was just 5e rules. They started with a D&D-DOS hybrid which was much more DOS than it is currently, and only after releasing the game to the public they were told by many players about all the shortcomings of their homebrew changes and began implementing these things closer to per 5e rules.
Edit: To clarify, it's perfectly fine that Larian literally did not implement every single D&D rule first; "all rules" obviously is an exaggeration. At the very least they wouldn't have all classes implemented in this first build, which again is fine. The problem is the sheer number of important rules that were clearly changed from 5e RAW on initial EA release, rules which realistically wouldn't have been implemented that way had Larian truly tried 5e RAW first.
