It is an intriguing theory, though psychology based theories always tend to be hard to prove - if they can even be proved at all.
A primary ingredient of that recipe being dissociation makes sense. But I might even suggest that this includes
disassociation. To sum it up briefly: dissociation is involuntary, whereas disassociation is voluntary. But they can in some cases result in similar symptoms. At the core of both concepts though is that disconnection from someone, something, oneself, or the world. Though a child may not necessarily be dissociative because they have not experienced a form of early stress or trauma, they may choose to disassociate depending on the circumstances.
As a rough example: a child who can't seem to find any other classmates who have the same interests as them might then choose to disassociate themselves from their classmates. They may feel disconnected from the concept of friends because of these circumstances, and that disassociation can then potentially lead to a connection with therianthropy. From what I can see, humans don't tend to function very well when completely disconnected. They need to be connected to something, someone, a concept, a goal, a philosophy, anything. And perhaps therianthropy is just one of those things.
In this way then, obviously those who experience dissociation are more likely to identify as alterhuman (and this has been seen on many occasions where those with DID have reported experiencing animal-like identities). But I believe disassociation can play a part too, which is not inherently dependent on neurodivergency, trauma, or personality (though may still be affected by such traits). Anyone has the capacity to disassociate.
And obvious disclaimer: I am not a medical professional, I am just guesstimating.