Thanks for the clarification.
This is actually working as “intended”. Gradle captures the output during tests, and associates it with the test case. Within a shutdown hook, there’s no test case to associate it with and nowhere else to send it other than to “the console”. This is the safest default as that output might be useful information, and there’s no other way to capture it.
It is conceivable that there could be an option on the Test task type to suppress any non test output from the test process.