Unfortunately the Sixers haven't been very forthcoming about all this so it's led to a lot of speculation and suspicion that he's not conditioned properly and that's the issue for why he hasn't played yet (it's not). I suspect the Sixers haven't wanted to admit he's still injured because they don't want to admit that he played in the Olympics and playoffs when he probably shouldn't have.
I know the old school train of thought for something like this is to keep all the information in-house in order to maintain as much competitive edge as possible, but as you kind of alluded to, a lot of this could have been avoided if the organization were more transparent about what Embiid's going through.
I think that transparency is particularly important now that these pro sports leagues have officially partnered with sports betting entities.
The OU football fan base has been going through a similar stretch in regards to fans turning on injured players. And it's all because the coaching staff chooses to be vague when it comes to disclosing injuries. A player is listed as QUESTIONABLE for over a month with a "lower body injury". Football fans expect someone with a QUESTIONABLE designation to probably play that week or the next at the very latest. So when they see someone still not playing over a month later, it creates frustration. If the player has a torn quad muscle or whatever, just admit it so that expectations are properly established.
Makes no sense to risk turning an entire fan base against players.