No, they haven't. Logo tees (Where it says "hollister" across the chest) are actually bigger than everything else in the store because they want more people to be able to fit into it. Everything else should still be the same.
yes it would be an xl at hollister. I shop both places all the time and american eagle sizes are one size bigger then hollisters because hollister sizes are rather small and tight and they do shrink slightly but not a whole size. I recommend ordering...
You probably haven't grown into it yet. However, the smallest sizes for Hollister are 0s and XS, while the smallest sizes for Aero are XXS and 00s.