Finally, Wizards clearly does not buy into any nonsense that just because D&D TT mechanics are TB that all videogame adaptations should also be TB. Not only have they explicitly said they intend to make other future D&D videogames that will use RT/RTwP combat, they are actually doing so with the Dark Alliance game which is RT.
Which is also a likely reason why WotC went with Larian, whose biggest bestseller so far is a TB game. If the system developed for Dark Alliance was so easily adapted for the type of adventure BG3 is meant for, they would have just ported the story, considering Dark Alliance is almost finished and close to release. Or they would have at least used that system as a base to build BG3 upon.
But DA comes with the limitation of having four predetermined characters (with predetermined classes) to play. And if I recall correctly, none of these classes are spellcasters, so likely they will have a more limited skillset, which can easily be mapped onto a controller and played real time. That is very different from BG3, where I can play a e. g. druid who has both several spells at her disposal and shapeshifting. I am not sure it would be even possible to have an ui which would allow to easily control all that in real time, without pause. Which leaves rtwp, but I don't recall any rtwp that have made it to the steam top charts and stayed there for as long as e. g. Skyrim.
WotC is part of a very large corporation, and I doubt they would have made any decisions without analyzing how well games using the different systems (real time, rtwp, tb) have been selling the past few years.