Just had some work done,normally I would dive in myself but I didn't have
the time and the job would have taken me a week or more...

I was interested to note that all the compression fittings the plumber
used have PTFE tape around the pipe extending from the fitting to a few
mm out.

I remember using tape around leaky olives a few times usually because
some enthusiastic "plumber" jumped up & down on his stillsons to get
things "really" gas tight.

My only thoughts are that a layer of PTFE between olive and nut on a new
fitting would lubricate the item a little and make it easier/ smoother to
nip up.

I have had the odd fitting or two that isn't to easy to tighten and makes
a noise akin to my knees in the morning when pressure is applied. Could
this be the reason for the tape?