The point is that comptime isn't dependent types at all. If your types can't depend on runtime values, they aren't dependent types. It's something more like kind polymorphism in GHC (except more dynamically typed), something which GHC explicitly calls out as not dependent types. (Also it's 12 years old [1]).
[1]: https://www.seas.upenn.edu/~sweirich/papers/fckinds.pdf