Yes it compresses, but, tape can certainly give an "Idea" of what is going on. 2 layers of say, masking tape, should be heavily marked or scrubbed off, imo.
Tape should not be used as a headspace gauge. If lacking the proper headspace gauge, I use the brass I am going to use.

As to the Federal factory ammo being or having excessive headspace as received, I've not seen this myself.

It is producing low pressure (and some headspace slop on that ammo) if the primers are backed out after firing.