Firewall question: is using a NIC with multiple jacks considered insecure?

[Quartz]

Some years ago I remember reading that when using OpenBSD (or any OS, 
really) as a router+firewall it was considered inadvisable from a 
security standpoint to have the different networks all attached to a 
single network card with multiple ethernet ports. The thinking being 
that it was theoretically possible for an attacker to exploit bugs in 
the card's chip to short circuit the path and route packets directly 
across the card in a way pf can't control. It was also suggested that in 
addition to using different physical cards, the cards should really use 
different chipsets too, in case an unknown driver bug allows a short 
circuit.

I swear I read this somewhere on the website, but I can't seem to find 
it now and I'm wondering if the concept is even still valid. The impetus 
here is that I'm building a router+firewall for a cramped location and 
it's turning out rather difficult to find a case that's small enough to 
fit. I'd really like to use an itx system with multiple onboard ethernet 
jacks and cram it into something like a MiniBox M350 or Antec ISK110, 
but I'm not sure if that's a good idea, security wise. Any thoughts?