Psilocybin treatment is given in a therapist's office in conjunction with therapy so, yes, there could well be very positive effects for patients having that therapy experience with a placebo.
At the moment, there's nowhere near enough research yet to know the potential downsides of using psilocybin to treat depression. So far, there's only been one study with 19 participants and no control group. It could be hugely successful or, as with any drug, it could come with possible side effects.
You're right - so Compass the for-profit has only filed an application for patent. But it's likely they're trying to patent a method of manufacturing the compound, rather than the compound itself (which, as you say, is publicly know.) As for the IP owned by Compass the non-profit, they didn't respond to comments on what that is, so it's not clear what exactly it entails.