The five creature_display->key->hrefs returned include only 3 unique values. (84570 and 81722 are returned twice.) (I was going to paste the whole response but I couldn’t find a way to make the long lines look reasonable on my screen.)
All returned hrefs within a single mount record would be unique.
This was hardly even a nuisance to code around, but since there is only one mount that has this condition, I’m reporting it in case it’s a clue to something potentially more worrying down the line.