Roadsters, GG2 is merely reminding that Joint is GREEN.
Daughter, a sqn ldr, used to get snotty emails and phone calls from the Adjutant (captain) about attendance at Army functions when she was in a Joint unit and no acknowledgement of light blue commitments.
As PMC she got her own back when running a dining-in night with RAF protocols. Yup, the Army was no where as sophisticated with no idea of passing the port.