By that logic, is it possible to play a game with several books worth of optional rules without house ruling it? GURPS has several dozen books worth of optional rules. Is it impossible to run a GURPS campaign RAW?
I don't know. Since GURPS is intended to be a pick your own toolbox sort of game, the most you could say is that you were playing with a certain set of books. But even then you'd probably having to specify which optional rules from those books you were playing.
I gave up at GURPS after a half-dozen sessions. I learned a lot from it, but mostly in the negative - how not to design a system, how not to justify a rule or rule set, how rules as read were entirely different than rules in play. Suddenly I learned why the hit point, the class, the level, no active defense, not stuns or injuries, no critical hits an a lot of other design choices that in the 80's I'd heard so many people say were stupid purely on the intuition that they weren't "realistic" where "realistic" really meant something like "a intuitive correspondence between the outline of the process of play and the steps being simulated".
Nah, usually we're getting a few things wrong at the start, and by the time we've figured out most of our mistakes the group is already starting to house rule. So, in any group I've played in I doubt I've ever played Rules as Written.