The different typedef configs allow for user specified comptime behavior regarding coercion, unified call syntax, member access, available syntax, restricted syntax, custom validation, etc.

C typedefs are useful for giving semantically meaningful names to lower-level types; however, C compilers don’t use these names during type checking and perform their type checking only on the ...

I believe your alternative is exactly equivalent, so the reason they didn't do it that way is just that they preferred their way for whatever reason. Presumably they found it familiar and readable and ...