Of course they can. We all know this. I had a number of house rules. But someone sets the standard that we all deviate from. And that standard should fly from the flagship product. When I was running table top games that someone was the tournaments.
The question I have is are they going to use the house rules talking pointas the thin edge of wedge to argue that the game should remain as DOS-D&D hybrid. I want to see something closer to the rulebooks, I think that would be more fun. Solasta is really fun and it's showing that you need to hybridize the rules to make them fun.
Sure the license is for the Realms and the rules are just "whatever the house decides" why not just use "Mae'rune" as your setting? The PoE world is essentially the Forgotten Realms after it had been taken over by atheists armed with artificer tech. I mean really -- that Sawyer's stated reason for creating his own setting, he didn't want to have to deal with WotC.