Okay here is the thing and it may blow your mind away, Tes Reality is not like our own, even if we like to compare it to it.
Humans have two distinct definitions in Tes, One for the races of men, but also for all playable races. According to an Uol source only 3 furstocks of khajjit have the unique male cat feature. Rest of the furstocks do not.
Argonians can vary, they can be either warm blooded or coldblooded they can lay eggs or they can give birth to live young and they can vary in appearance they can even have feathers like a bird. Some even looking more human. An argonian female can give birth to a child from a human or elven pairing. We have a in lore example of this in a history book.
https://en.uesp.net/wiki/Morrowind:Generic_Dialogue_H this is dialogue from Morrowind, there is two distinct terms and definitions for human. One is used for all the races including Argonians and Khajiit then the other is used for the races of men.
Sloads, dragons, and other sentient races cannot mate with Men, Elves, or Beastmen, and are not considered 'human.' Exceptional accounts of matings between men and daedra do not fit smoothly into this scheme. Elves consider themselves the only 'truly human race,' being descended directly from the gods, and regard the Manish and Beast races as highly intelligent animals. On the other hand, Imperial scholars consider Men, Elves, and Beastmen as 'men,' on the basis that individuals of all three groups can mate with one another."
Like I said its not like our own reality, Argonians and Khajiit have unique variations. In fact in real life there is lizards that can do both egg laying and live birth and even at the same time lay an egg and give live birth. This is the trait Argonians have.
Argonians are unique in that they have mammalian, bird and lizard traits. Khajiit are unique in they can take up many forms and only three of those forms have the barbs. So most many look like cats but only three furstocks have the unique male cat feature.
Lycanthropy is not a racial condition, the condition is unique in that there is basically an animal like spirit attached to the lycanthropes soul. This is how they transform into that respective lycanthrope. I suspect its a vulnerability some can use to mind control other lycanthropes and even change their personalities. We see examples of this in Eso.
There is one Khajjiit origin story and and one thing talking about something similar for the Bosmer that got removed from Eso that refers to Hircine actually being the possible ancestor to both the Bosmer and the Khajiit. So both those races are related, and techically this would make Bosmer more of a Betmer then an actual mer. Though Bosmer have intermixed with Ayleids which might be why their blood counted towards the one quest in Skyrim and why Ayleid blood was not needed.
This would be before Azurah and Y'ffre changed them into the Khajiit and Bosmer respectively. Interesting trivia there is a possibility the wereshark is a khajiit lycanthrope. Both Raz and MAiq have claimed to have encountered that particular lycanthrope.
So the gist of it Khajiit and Argonians are not like our cats and lizards. They are their own unique thing, and they can be infected with all kinds of lycanthropy. A khajiit can become a wereshark, a argonian can become a werewolf. This is a lore fact, this is how Bethesda has decided to do it.
Just to note, its widely accepted that Azurah is the "Mother Cat" in Khajiiti lore. If Azura did indeed create the Khajiit then the Race is off limits to Hircine. (minus the curse that is)