The distributed lock uses the localTime field of the serverStatus command to compare the clock skew between the local time and the remote time. It also take into account the amount of time for the command to execute (delay) and subtracts it from the raw delta.

If the delay was big enough in the test, it can lower the average skew such that it will be within the 30 sec skew tolerance, making the test fail because it expects the movePrimary to fail because of skewed clocks.