SG may well lead to a slower journey, but not for the person sending SG, it may well be another train...whilst the Signaller wanders over to the GSM-R to see who the beep is
One annoying thing I hear some Signaller say, is that they get SG, and the train is booked the stand there some 90 mins ! (we have a freight booked to wait on the Bacon Factory for over 90 mins, but they send SG as they approach the signal) would be nice if the Signaller could send back a bit more than just the 'wait' that is the standard message !
Oddly, that is when the Signaller may not get SG ! something we find quite odd, you can stop a train at a signal that is 'never' red (normally), but utter silence from the train