For a long time, I never thought I could be a physical alterhuman because all I knew about physical alterhumans was they experienced physical shifts, and from what I know, I neither physically transform nor experience clinical lycanthropy. However, I've learned that not all physical alterhumans can be boiled down to just "physical shapeshifter." Some are always physically their 'type. Some have genetics of their 'type. Some simply assert that because they're nonhuman, so is their body, no matter what its external shape is.
All this to say, I think I might be in the genetics camp. I'm a descendant of Hati Hroovitnisson, one of Fenrir's pups. My dad told me I have Irish heritage, explaining why I'm a selkie- and it's likely my lycanthropy/cynanthropy comes from the intersection between those lines, as I have a theory the Werewolves of Ossory (you might know them from Wolfwalkers, but they come from a real werewolf myth) were Pagan Norse-Gaels before the story was Christianized. I relate my cynanthropy in specific to my theriform black GSD sister, who was my dad's dog. My dad was also a psychic vampire in his youth, and while I don't think I have vampiric powers, I do feel a connection to vampires (vampirehearted?) and have a bat kintype. I fully believe that at least some of my kintypes are physical in that they are genetic, likely on my dad's side (though I wouldn't be surprised if my mom also has some critter in her), and I am likely a 'dormant'/non-transforming werebeast, explaining strange sensations I've experienced that aren't quite phantom shifts and my urge to transform.
I'd be interested to hear other physical alterhumans' perspectives and if this makes sense. I still don't know everything about this label, and could only find resources for physical shifts when I looked up the term, so it would be nice to find some proper info on this aside from just others' accounts.