The website says ALL self guided tours require reservations of at least 3 weeks, however when you click to put in the reservation, it says you only have to reserve groups in advance... Which is it?

That was required but not anymore. You can just walk in now, it’s a new change but you don’t need advanced tickets.

I did not go in a group, there were just three of us. We did not need reservations.

We did not make reservations and purchased our tickets at the door.

when I visited last week I entered directly without booking. That may be for groups in advance. You can make a call to have a conversation directly if it works for you.