When hotspot team started to adopt ProblemList as a way to stabilize testing several years ago, one of the final goals was to run problem-listed aka "quarantined" tests separately from other tests. This should allow us to reduce the level of noise signals and at the same time gather more information about these failures and not to miss coverage from "quarantined" tests as there is evidence that they can find other and usually more important bugs in the product.

Conversion of vm-testbase tests to jtreg format increased the number of problem-listed jtreg tests and therefore made it more probable to miss important bugs. That and ongoing activities aimed to reduce "noise" in CI are somehow making this a higher priority again.