"Stefan"

(Bombardier facility and military base) has a tower (in the physical
sense) with an operator that replies "cleared to land at your discretion"

This is a contradiction in itself. This operator musn't give any
clearances and hence musn't use the "cleared". It is very important to
understand this.

The "operator" can't give the kind of "clearance" ATC gives. But they can
grant permission to land and I don't know of any regulation that makes it
illegal for them to use the word "cleared" when doing so. I've never heard
them say "cleared" without following it with "at your discretion". They're
talking to pilots who are required to know that a Unicom is not an ATC
facility. And sometimes they can give or refuse permission to land (private
facility) and sometimes they can't (public one).

moo