I think there is some confusing and/or misunderstanding.
Still I would not recommend people to modify their Gradle project configuration, when the only issue is about the single sonar task. Also the statement about this approach being “equivalent” is not true from my perspective.
Sorry, maybe I didn’t make it clear enough, but the error message in the quote only occurs without adding –no-parallel.
So the initial workaround by just adding no-parallel at task level should be enough and was actually provided by a Gradle employee for an different plugin that faced this issue.