We are in YC. Today, DD and I were at SAB. When we returned, we had new locks (the part where you place your MB). DW was in the room when it happened and said they did not need to open the door.
Also, we do not normally have housekeeping clean the room. DW has been in the room napping once when they came by for the "security check." She said it was a light knock on the door (she barely noticed). She went to the door, and they told her that they were there for room inspection. However, they did not come in the room. Today, they called to ask when they should come by for the next room inspection (since we told them we don't want housekeeping). Our experience at YC with the security check has been very unobtrusive.