Is it true that pigs are "melting pot of flu viruses"?

[teo123]

I've read the claim that pigs are "melting pot of flu viruses" on a few places on the Internet, some of them not apparently related to veganism. The argument goes that, due to the way pig immune system works, pigs are relatively easily infected by both mammalian flu viruses and bird flu viruses. So when a single pig is infected by both a mammalian flu virus and a bird flu virus, those viruses can "mate" by infecting a single cell in that pig and potentially create a new dangerous strain of the flu.

But how does that make sense considering that flu virus is haploid? Viruses can "mate" by two different viruses infecting a single cell... if those viruses are polyploid, that is, if their genes are stored on multiple molecules. But flu viruses aren't like that, their genome is a single RNA molecule.

[teo123]

For example, here:

Pigs are susceptible to human and avian influenza A viruses; hence, they are believed be effective intermediate hosts for the evolution of new viruses with a potential to produce pandemics. This occurs because the swine serves as a melting pot to generated new hybrid viruses after genetic resortment.

[teo123]

I've asked this question on Skeptics StackExchange: https://skeptics.stackexchange.com/q/57539/56242