Nonissue having the working students/assistants warm up the horses. I was doing that in the 90s as well in a show jumping barn. It was never illegal at HJ shows so I did it at shows too. In fact I often did the jump schools too, especially on the young horses who just needed to go jump around once or twice and see the new fillers in the morning. We’d each take a baby green and get through twice as many horse preps that way. But it was legal, key.
I feel sorry for CP having to do that, but I must say I willingly got back on within a week of childbirth and I’m just a lowly amateur with horses at home. As soon as I could pawn that baby off on Grandma I was back on a horse. I didn’t tell my OB when I got bucked off immediately, either! Note to self, when the young OTTB has had a few months off and your core has been destroyed by a 10 lb human growing inside you, LONGE FIRST.