Semantics
Spitoon
You are arguing over semantics and not the services provided.
For instance a Flight Information Service (noun) is a service facility from whom you may receive a service (the verb). You may, of course, simply ask for an answer to a question even when a service is not intended to be ongoing.
To answer your question of me. An Air/Ground Service (noun) is a facility which may often or never be manned, so could not therefore offer a service (verb) to the pilot. Those permitted to operate the ground station if and when it is manned are only required to meet a minimum level of competence. They are permitted to provide specific information which is known such as the runway currently in use together with the circuit pattern and the altimeter settings currently in use at the airfield. Nothing else! They should be able to answer questions such as the fueling and parking arrangements and other elements of the aerodrome manual, on which they are assessed.
An Aerodrome Flight Information Officer (AFISO) is trained and tested to a higher level and is permitted to control aircraft on the ground but in the air even within the ATZ they may only give information. They have demonstrated their competence to keep a log of movements and therefore they may pass that info to the pilot. i.e. " G-ABCD you are number three, report final". They may NOT clear aircraft to land. AFISO are also tested on the use of all tower equipment available such as approved wind and altimeter setting machines etc.
You asked me for the source. The source is CAP 413. Other sources are those publications for the training and testing of Air/Ground Operators, AFISO and ATC Officers.
I agree the current version of CAP 413 is appaling and is not helpful. Earlier versions were much clearer in explaining the different services within one publication.
The new document CAP 774 is very helpful in explaining the services in detail. There is in my opinion very little that changes from today (within the UK) other than in names such as; BASIC (FIS), TRAFFIC (RIS) and DECONFLICTION (RAS), the letters in brackets are mine . The UK has provided all this for years although much of it will be new to the rest of europe.
Reading about the individual services within CAP 774 will give everyone today a very clear understanding the present system in the UK as well as from next year.
The biggest weakness that candidates for the RT Test demonstrate, to me, when undertaking their RT test is that they do not understand the system. The RT test is about the use of the system as much as it is about RT phraseology.