So if adaptation is good it can be considered as canon/ continuation and if it's bad it cannot? What kind of logic is this?
In the first place it doesn't makes any sense bring the movies as we are talking about the games and if they are a continuation, they are very different things. Yes, he gave his permission to both, but their similiraty ends there. The game is a master piece who represents with a lot of fidelity, mainly in terms of quality of the storytelling but also the lore, what was wrote by Sapo in another media. The movies doesn't reprent 10% of the greatness of the original storytelling quality and the lore, they were shitty low budget movies made without much effort. They should represent the lore, but it can't. Just take a look at the costumes, weapons, the golden dragon CGI and cast... It's not a matter of good or bad, it's a matter of representation AND quality.
Which one do you think that is closer to the greatness in terms of quality of the original work? Which one do you think that is as great in storytelling compared with the books? Which one do you think that portrays better what Sapo created? How can you compare such an amazing saga of novels as The Witcher and one of the best games ever made as W3 to those (with all do respect) shitty low budget with terrible actors and CGI effects movies that no one watched? It doesn't makes any sense. There are people who consider the movie an "abomination" compared to the amazing original work. Different from the movie producers, CDPR putted a lot of effort to make it as good as the books and as close as possible to the greatness of the original work, that's a logical way to compare and this is exactly why I said you can't put the games as an ordinary "fan-made", like it's the same thing as the movies. There is an obvious difference between a shitty fan-made movie and a master piece who pratically represents the books in a 3D world, and that is very close to the greatness of the original work...
It occurs to be exactly the same in TV series, and comic books also.
Now you are bringing another media lol. The comic books looks amazing, I read a little and I felt that the original work was represented there, including the lore and characters. But, do you ever watched the movies? I didn't, but as far as I know there are tons of holes not only in the script quality but also in the lore representation, probably cause of the low budget. Including swords, costumes, characters development, the shitty special efects etc etc. So no, the lore representation is poorly portrayed and W3 is in another level when it comes to lore representation.