Apple AASP demanding "diagnostic fee" for warranty service

I'm trying to obtain warranty service for an iPad Pro still under factory warranty. I'm in a country that only has AASPs and no Apple Stores at all. The AASPs (all four of them) are demanding a $30 "diagnostic fee" to even look at the device. When confronted with the fact that Apple does not charge "diagnostic fees", they responded that it is "corporate policy" of the AASPs.

My question is: is this practice condoned by Apple? And if not, what's my best course of action now?