Why do you think that Larian changed certain spells functionality?
Because despite the fact that Larian asked to get permission to make a BG game and the fact that BG games are based on the established ruleset found in DnD... Larian very clearly wanted to make their own thing.
Between all the homebrew and their statements about how "Restrictive" the DnD ruleset is, it's very apparent that Larian wanted to make their own game that uses their own rules and that the BG IP itself means nothing to them besides a way to gain popularity.
So they changed the functionality of various things. Often to make them even more powerful (Haste giving a complete standard action, including for spells. Tavern Brawler affecting throwing weapons and unarmed. Fast Hands allowing for ANY bonus action instead of just a Cunning Action. Etc.) because it's what they wanted to do rather than anything to do with its ability to translate accurately into a video game.
Which is honestly why I don't buy their reasoning for capping out at level 12. The problem of "Spells being difficult to translate into a video game" argument loses weight when they so clearly homebrew so much of what they did include anyway.
