and think it's ok to distribute the /xt directory (or author-only tests)

I agree. Even if the tests are never run by someone else, they might still prove a valuable resource to another author. And if (somewhat unexpectedly cause my code is always perfect) bug reports start flooding in, it is always a good thing to have all existing tests for the distribution already deployed. It's much easier to ask a user to "just run this command(s) and post the output" than first having to haggle about how to send the test scripts and set up the test environment.