I'm not a huge fan of hybrids (not usually a fan of locality crosses in other snake species either) however some are naturally occurring.
Amazon Tree Boa x Emerald Tree Boa have been found and collected in the wild
Bullsnake x Foxsnake, I believe some rat snake subspecies have been found as well
I think most of these are all the same genus however and obviously naturally occur in the same area.
As long as the animals are honestly represented, to each their own IMO