When I was instructing early students one of the first things I teach them is the status of the A/G (or AFISO) at the aerodrome concerned. I never refer to the "Tower" or "Air Traffic" in this instance. I use phraseology such as the "personnel who work in the building over there...."
It is important that pilots understand the "service" which they are in receipt of.
Agreed, and this should be obvious from the telephony designator used on the R/T. What they say on the phone when you're filing a flight plan or booking out doesn't matter so much, but I do accept that it should not infer a different level of serivce from that being provided.
Please remember that a FIS is, de facto, an air traffic service, so why can't a FISO refer to himself as providing such?