That's the whole point. They would not hold it. I could mail the request to them. I could hand it to them in my local office.
I complained to the Postmaster at the local office on numerous occasions that they were not holding my mail as requested.
I retired from US Civil Service myself and never heard of anything like this.
When it dawned on my that if I just left the mailbox off the Tee I had installed in the driveway of the pad and just set it in the garage while we were gone there would be no place to deliver the mail.
That worked and confused them at the same time.
Thereafter I just pulled the mailbox and left it in the garage. When we got back from an extended trip I went to the PO, picked up my mail and they started delivery again.
We did this for 5 years until I moved from that location.