I've reported this informally before but couldn't find a record here or in IssueTracker.

When jtreg converted from using JavaTest 3.2.2_02 to jtharness 4.1.3, there was a significant change in behavior: previously, the core harness would only read the tests that were given; now it always reads all tests in the test suite, which is made evident not only in the final report, but also in the time taken to complete what might otherwise be a small jtreg task.Users have noticed the time taken, and the users are not happy ...