After searching the mailing list (and the web in general) what I can gather about multiple PTR records is that postfix is adamant that hosts should not have multiple PTR records.
Who cares? It's like saying DNS names should not have underscores or spaces. Yes we don't like it, but it's easy for postfix to accept and deal with it. OTOH, it's difficult to get OTHER admins to fix their configuration and additionally it doesn't actually create a problem that I can see. I'll post my actual problem in another thread, to keep this one focused on the policy around multiple PTR records. -frank