The new MOS just says that one of the functions of a CA/GRS is to provide:
"advice on relevant air traffic in designated airspace or on the aerodrome",
But nowhere can I find any reference as to what constitutes "relevant" traffic. Relevant is a very subjective term. Back in the day, the old AOI (Vol II) had very concise standards to be used for assessing what constituted traffic. I bet the guys in PHD providing an AFIS work to standards. The MOS is much more precise on what other information a CA/GRO can provide but traffic seems to be "whatever you reckon".