I really don’t like the idea of anyone putting their hands on a horse to judge if there is blood there or not. It reminds me of grade school: You look with your eyes. Why are you touching/rubbing to “see” if there is blood?
I’m not saying that it was forced in this particular case. And perhaps I’ve read too many novels…but it seems like an easy enough thing to have a needle/tack in a glove to force a puncture and disqualify a team/country.
I, like others, have seen dripping blood on legs/hooves, under tails from crupper rubs and other places without issue.