It all depends on hotel staff (management, really.) I don't remember where I got this from, but I recall that for most(? all?) properties, there is no direct link between OLCI and their property system. Someone has to check the app website/messages separately and input those into the property system manually. If they don't, you don't get it. That makes no sense to me, but given the observed behavior, it does track.

I probably have a successful OLCI (meaning processed) about 50% of the time. I get a mobile key from OLCI probably 10-20% of the overall time. I always* stop by the desk to get a physical key, anyway, so the OLCI is not as crucial, but still helps. If the property does it right, then the in-person experience is greatly shortened. Quick ID check, confirm welcome gift, off I go. That's generally not the case, unfortunately.

*I have a documented case somewhere in these forums of a successful OLCI with mobile key delivery where I didn't stop by the front desk. I think that's the only time, and that was only because it was a very quick trip.