I feel like this should be clarified a bit since it might give some readers the impression that visiting the lobbies is something that could be “challenged”! I don’t think there are exactly rumors of anyone being challenged entering a lobby; visiting the lobbies is encouraged (how else will they sell their $20 shot glass cookies?!).
The only place you can’t enter is into the GCH from the main entry (so, coming from Paradise Pier, basically, where cars drop off for the lobby). They do routinely have people stationed on the street there to prevent anyone but GCH guests from coming in. It’s not at the lobby, really, but on the street.
We had a Napa Rose reservation when my mom was in a wheelchair with an oxygen tank and we were walking over from the Disneyland Hotel, and they still weren’t going to let us through there until my husband forwarded me the email for the reservation that he’d made. We also noticed they had people stationed there when we stayed at Paradise Pier this June. So that is a thing, but it’s just that one entrance.