It's my understanding that there are two different ways to get lounge access:

1. As an elite benefit, currently for Marriott Bonvoy Platinum Elite and higher, regardless of the room type, as long as the stay is eligible for benefits.

2. As a major benefit of staying in a room type that's identified as "Club Floor" or "Concierge Level" or any other category that includes lounge access as a feature of the room — regardless of status, and even if the guest is not a member of Marriott Bonvoy at all, and regardless of how the hotel bill is paid.

If my neighbor, who is not a member of Marriott Bonvoy, decides that a Concierge Level room is worth the higher price compared to a standard room and reserves such a room, then my neighbor (and anyone else legitimately registered to the room) gets lounge access. I don't think anyone would dispute that. After all, lounge access is a published benefit of the room type.

Along the same lines, it seem to me that if any guest is upgraded to a room type that officially includes lounge access as a published benefit, regardless of status, then that guest gets lounge access. It's a feature of the room.

If a hotel does not want a non-member, basic member, Silver member, or Gold member to have lounge access unless the guest is paying for room type that includes it, then the hotel should try not upgrade the guest to a room type that officially includes it. But it a guest receives such a room anyway, then let the guest have a few mini-eggrolls in the evening and a plate of self-service breakfast in the morning. Not allowing it is an insult.