This failpoint was introduced in SERVER-90465. Currently, it allows movePrimary to move all client system collections other than system.bucket collections. The reason is that based on how isAlwaysUntracked() is defined, in particular here, moveCollection doesn't support moving any system collections other than timeseries collections. The failpoint couldn't just call on isAlwaysUntracked() because it needs to allow movePrimary to move the ".system.resharding." collections created by the fuzzer since moveCollection doesn't have a way to tell that they not a real temporary timeseries collection so they are just by design rejected by moveCollection (this test case). This ticket is to investigate if we could add the system.resharding collections as a special case and call isAlwaysUntracked() instead of isLegalClientSystemNS(). So we are sure that we only allow collections that can never be tracked to be moved by movePrimary commands in the config transition suites.