Correction: it is in fact hearsay but it is admissible under one of numerous exceptions to the rule that hearsay is not admissible.

Laws are generally clearer if you write them as general definitions and general rules and if those cover too much carve out exceptions in the rules rather than the definitions. It would work to make the exceptions to the definitions instead, or to both the definitions and rules, but that is usually going to be more complicated and less clear.

For hearsay the general definition is "an out of court statement offered to prove the truth of what the statement asserts" and the general rule is "hearsay is not admissible", and that is narrowed by a bunch of exceptions to the "hearsay is not admissible" rule. As far as I remember pretty much everyone has left the definition untouched.