Single incumbent position with multiple employees

Hi All,

We have a position of type "single-incumbent" and there was an Employee hired to this position. However, after several months, there was another hire and the new employee was also tagged to the same Position. We expected an error or warning with position headcount. But surprisingly, there were no warnings and system let us hire the new employee. Now both are tagged to the same position (still showing as Single Incumbent).

Only difference between the two worker assignment records is that the 1st employee's assignment had the position synchronization turned off. Does that allow the position to be used for new hire? Any thoughts? Kindly advice.