Bloggsie,
That is a dopy expression, that emanated from the same "source" as that equally dopy readback "XXXX coming down - callsign", as a read-back of a transponder code change. Such affectations grow within some carriers, nobody has ever suggested they are "appropriate", because both example do have standard meanings and read-backs, and are not a subject for ad-libbing.
Re. the Manual of Radio Telephony, most of that is
how to do it, the consolidated list of standard phrases and meanings is (as I have previously said) mercifully short, one page in the Jepp. format.
At least, with the spread of datalinks, I no longer have to listen to the tortured non-standard (that is, not in accord with Annex X, Vol. 2) positions reports from VH- aircraft, conforming to said pedantic, inflexible, one-size-fits-all and non-ICAO compliant Australian "radio procedures".
Tootle pip!!