We used to do import('@wordpress/element') and now we do import('react') for RefCallback. I'm curious if there's a good reason for that.

@wordpress/element doesn't actually export all of the types needed, so importing directly from react is better/more consistent. More discussion here: #31603 (comment)

Also I tried to look up RefCallback but couldn't find anything. Any pointers?

RefCallback is the style of ref prop that goes like: <div ref={ node => { /* do something with node, probably assign it to this.something */ } } />. The type is literally just a function type but with a specific name used for ref props (as is the intended usage of the return type of this hook).

Do we really need never here?

What would you suggest in place of never, if the template type doesn't extend Ref? never is essentially the error case for this utility type.

I understand, then never makes sense 👍

What is T?

T is the type of the ref. I could rename it to TRef if that would help? I wish we were able to pull out the type parameters into the generated docs, maybe something to add to the docgen feature request list.

I agree that having a more explicit name would be better — TRefsounds like a better alternative

T is very common in the TS world, but yeah, I think having a bit more specific names can improve readability.

What does T stand for? Type? Could we avoid abbreviations? What about RefType? Isn't that much clearer?

T stands for Type yes, its the canonical abbreviation for a generic type. Adding T to the front generally indicates its a generic type as well, so TRef is appropriate is more appropriate than RefType which could easily be confused for an actual type rather than a generic type parameter.