I know past the Main a Neutrals not required but this is on the secondary side of a Transformer. Yer taking Ground off XO of a transformer???? I feel it should be called a Neutral, Landed on a Neutral bar Bonded to Panel then Grounding Electriod run to that bar. Its really the same but called a Neutral.
If there wasn;t a transformer on the other side then Calling it a Ground would be no problem.