Not if their goal was to make the non-mobile version of their site usable on your phone. But if their goal was to make the non-mobile version of their site unusable on your phone, they did just fine. (Why would they want to do that? To encourage people to use the mobile version. Why would they want to do that? Among other reasons, to make them use the Messenger app.)
Yeah, that's pretty conspiracy-theory-y: it implies that Facebook did something that was unequivocally bad for user experience, in order to push people into interacting with their services using the methods they prefer. But then, disabling messages in the mobile website to push people into using the Messenger app fits that description perfectly too.