If the loop has a doggie poop bag station, it is a designated pet loop. If not, it is an alternate pet loop.
In simpler terms, every loop can be a pet loop, just some more so.
It's 2:00AM and we leave for FW and Marathon Weekend in 3 hours so I could be totally wrong and if so I attribute it to lack of sleep.
Well I can confirm that the 400 loop has two doggie poop bag stations one about 3 sites down from the walkway to the comfort station and the other a site or two from the exit from the loop. We walked our four legged friends every day and made lots of doggie poop bag stops.
on edit OOPs my locations were off by a couple of sites, but yes that is where they are and why would disney have these in non pet loops.
Larry
Larry