UA has a lot of personal information about you...name, birthday, passport number & date of birth (if you've travelled internationally), credit card number(s), travel history. I really don't see the problem with giving them your transcript. Grades won't exactly enable identity theft, either...

UA will accept alternate forms of certification:
copies of diplomas (mine's in Latin, though, so I'm not sure they'd want it!)
certification letter from Registrar's office--this is probably the best non-transcript option