That's certainly a factor.
Another possible factor is that the author of the remastered MD5 models is Capnbubs, who started doing those models in 2013
Link. The skin of the grunt in the remaster is exactly the same, with an added muzzleflash, and the dog skin is 100% the same.
Back then Capnbubs already mentioned working with an skeletal model format, which may be the MD5 format itself. I don't know when the IQM format was created.