Timbers and coppers live together in Kentucky as well. I have seen them huddled together in dens or underneath fallen trees. In my opinion it is not a bad thing to house animals together in captivity that house themselves together in the wild. As long as they are not predatory against each other or ill from overcrowding and stress.
EDIT: To go off what Bcr229 said, I do think the enclosure was extremely small if it's only 3x3 but then again I wonder if that is only a temporary display and if the animals are moved into larger enclosures away from public eye. I am not picking a side on the debate, because I know nothing of zoo practice. But I think there is a lot to be learned on both sides. The zoo perspective as well as the personal hobbyist or keeper.