If introduced properly...most IPO dogs will bite something other than a sleeve. You can basically trick them into doing it and once they do it once, realize its okay, they'll keep doing it.
The reasons its not done were listed by hunter...
I work in SDA and in IPO, and you realize dogs will bite whatever you train them to bite. They'll also have their favorite spots...which is what you tell an SDA helper before you trial, so that they know what to present to the dog for a bite. So even on a coat...my dog bites the forearm.