Not mandatory but recommended Stuart. It’s not mandatory because it can be found on Sotawatch most of the time.
So is grs for grams. Grams is just g
According to the GR, 220.127.116.11, …QSOs must comprise an exchange of callsigns and signal reports, it is strongly recommended that the summit identifier be given during each contact. Where the summit identifier is not given in each contact (for example in slow CW QSOs) it should be repeated frequently every few QSOs. Note: Summits are commonly misidentified by chasers when “spotting” on the SOTA Reflector. Ask the Activator for the summit reference if you have not heard it stated.