I can say that back in late 2021/early 2022, when the ships were sailing at 10-20% capacity and we had maybe 20-30 people in Yacht Club, I was able to get permission from the Concierge to escort a few people through the YC facilities as a kind of "show and tell". They always said it was fine as long as they did not use any of the services, i.e., drinks, food, and we were out in 20-30 minutes. I think they were allowing it as they were desperate to get the ships, and particularly YC, sold out again.
Recent cruises the ships have been so full I have not even asked. But I also have seen two instances in the last nine months of people getting escorted out, once on Meraviglia and once on Seaside.