I believe they can reset the safe and open it with their master code.
Although usually need higher lv staff not the housekeeping team to do.

I think its ridiculous for a property to reject an guaranteed elite benefit.

I believe I got rejected before at US Grant San Diego, but I take it as the particular FD didn't pay attention about elite benefit and my status.
After asking some other staff, the hotel agree to give me the late checkout required.

Never have issue at my other stays.
Hotels in APAC and EMEA regions tends to proactively ask if I need late check out.