We disabled logs when metal pipeline was enabled as it was causing some jtreg failures under : https://github.com/openjdk/lanai/commit/501ace02 .

Phil mentioned that we still need to print metal pipeline enabled log when vm option is set. Refer : https://mail.openjdk.java.net/pipermail/lanai-dev/2020-December/000778.html
Also i think using stderr for output might also have interfered with jtreg tests.