I bet among fans of the original games, many are pure video gamers who don't much care for how "faithfully" the games represent the tabletop rulesets, or "how many rules were bent" in the making of the games.
There are TONS of these fans. Way more gamers who don't play D&D (who for years have never even heard of the tabletop game) vs gamers who play D&D. This is why the BG series was so popular to begin with. Simple math...
There are STILL way more fans who are gamers who didn't, don't currently, and will never play D&D, than gamers who play D&D. Way more.
And here's the thing Larian and even WOTC surely know... but are still hesitant to admit....
MANY of those fans probably WILL NOT BE BUYING BG3: - if it's TB - if it's overly muddled and SLOWED DOWN by an engine that tries too hard to incorporate elements from a tabletop experience that they NEVER CARED ABOUT - if it's significantly out of "character" for a BG game.