I think that the landowner has "requested there be a single entrance". To what extent that has or has not been suggested to him I know not.
When Draenen was first opened up, the land was owned by the Coal Authority. Before an access agreement was later signed, their view seemed to be to keep things unofficial so that if there were some kind of incident, they could deny any knowledge that cavers were crossing their land. Cavers had been wandering around that land for more than 30 years (a least) by that point, discovering caves, digging open caves, surveying caves etc! The only proviso mentioned was 'Don't go digging any more holes on our land.' Of course, Draenen had an open entrance when first investigated by cavers in the '60s so was never a surface dig. The no digging on the land policy was later included in the access agreement.
At the time the cave was first opened up, the current landlord grazed sheep on the land, with the agreement of the Coal Authority. Some months after the breakthrough, he discovered a surface dig on the land. I had a look at it at the time and it was very minor, just a few clods of earth pulled back in a small depression. He was very unhappy with it though and told us that if he came across any more digging, he would make sure the Coal Authority refused cavers permission to cross the land to access the cave. This was well before the PDCMG or a single entrance policy had even been thought of.
Of course I'm not saying that some cavers haven't played up these no digging/opening up new entrances, wishes of the landlords.