Support mains in autofill

Just got out of my second queue this week where there were three support mains in one lobby. The first game none of them got support while someone else got autofilled onto support. The queue i just dodged out of had people threatening to disrespect the roles they got assigned to steal support. wtf is going on here, i thought there was a support shortage and that's why people were getting autofilled.

Autofill isn't working as advertised.