Type vs. Refinement

[67726e]

Per the documentation, "For example, you might want not just a string, but a specific format of string" is the prime example used for a refinement. However, the email type seems to match the definition of the refinement. Should the email not be used as a type but rather as a refinement?

To make this issue actionable, I think it would be beneficial to have a run-down of "Why?" in regards to Type vs. Refinement rather than just "Here's a type and here's a refinement."