I don't read it as _bypassing tests_. They have tested the interpreter (`template type`) when it was first released, and they have _validated_ the new template instance (via `content validator`) and assumed this is enough, because it was enough in the past. None of the steps in the usual process were bypassed, and everything was done by the (their) book.

But it looks to me there's no integration test in the process at all. They're effectively unit testing the interpreter (template type), unit testing (validating) the "code" (template instance), but their testing strategy never actually runs the code on the interpreter (or, executes the template instance against the template type).