You've got to be kidding. The version offered on Game Pass is the "Standard" edition, that isn't just a "free to play", "stripped down" version of the game. It is 95% of the game! The remaining 5% is almost always cosmetic items, like skins or cars, that really do not impact the core experience.

There are some exceptions, like Destiny 2 I believe, where the meaningful DLC is excluded, but that is not the rule. Game Pass is an incredible deal.