The eldest are crystal pony derived. We have pegasi, earth ponies, and unicorns now as well thanks to that whole maretonia issue.
The diamond dogs have a rough idea what to look for. We don't know what healthy adult hippogryphs are supposed to look like, so paranoia is important.
Also they're a hybrid, that means the potential for cross population disease and parasite transfer just went up a notch, we need to get ahead of that.
I'm not saying we should do anything weird or crazy, but we have to start assembling medical data on them soon. This isn't some extant race coming in and joining up already having a general idea of how they function. Hippogryphs are an entirely new species afawk and thus are missing a lot of the basic self knowledge and lore of their parent species. The empire created them, it's the empire's job to help them catch up a bit.