Correct. As mentioned, the ground crew obviously need to be aware (beacon ON, etc.) It also saves time on pushback if needed: start no.2 in H mode, disconnect and remove GPU, then request push and start; then start No.1 during pushback, then release prop brake.
H mode also means air conditioning, a plus if you are sitting on a roasting (or freezing) apron waiting for pushback clearance...
Cheers
