Well and Wolfheart has meet Larian.
That is true ...
But he also said himself that he didnt get any internal information ... i beleieve he said something like:
"
When i get into Larian studios Swen himself asked me what i want to know ... and i said tell me only things that are either allready confrimmed or subject of this upcoming patch ... bcs i wouldnt be able to speak about anything else i learned there, since that would be violation of NDA(?)"
Just paraphrasing ofc.
So his speculations and guesses are as good as anyone of us.

Well you can call this conspiracy theory if you want.
How come both me and him has come to same conclusion without even that video? From earlier information said. Well and if he guesses wrong then so be it but I would say his guesses are likely more then 90 % true for sure. No I am not going to bother search some more links to you as I did already provide something and not my task to do that.
Guesses only? Larian has said that they will keep and deliver PHB classes and subclasses (at least mostly anything outside it in classes and subclasses I take as happy and welcome surprise of course). Well and if he tells some info that he should not tell us that is between Wolfheart and Larian.
As I see it Wolfheart and Larian are in symbiosis (it means they benefit from each other). He has defended Larian also against some negative reviews fo BG3. I agree with his defence. Funny BG 3 reviews some lies said about what has been promised. Well and this game is not some fake project. I absolutely believe BG3 will be released during year 2023.
Sure you can call that video guesses, but I believe it to be true. Some things he does mention like this is not in Players Handbook so very unsure if it will be included I think he mentioned about Death Domain Cleric which is not in PHB. Well and personally I would be delighted if Twilight Domain Cleric would be included, but I doubt that and my guess it will not be in full release date at least.
An expansion could of course of course later increase level cap and bring more Dnd features such as classes/subclasses, cleric domains and races.
As for patch 9 please add Paladin class that is my highest wish.
Actually I must say if they would add Paladin class and rise max level to 5 in Alpha both these things I would forsee a huge increase of people returning to test BG3 again and play it in Alpha. Well so I have never said I am against level 5 in Alpha. A warning though Larian is perhaps preparing to finish this game in 2023 and do not bother to release level 5 in Alpha. Level 5 has not never been promised to be included in Alpha. I have said indeed I want Paladin class released as most for Patch 9 if I can only choose one thing for Patch 9.