Redwood Seniority dates page shows different behavior for Bargaining Unit field

Summary:

when we logged with custom HR Role user for seniority date RUI Page(dev2) and select any employee who is having more than one bargaining unit, then in RUI it shows the latest bargaining unit value as default in the field but when we logged with the same custom HR role user and opens redwood seniority page(in dev5) for the same employee who is having more than one bargaining unit, then in redwood it shows the value populated as per the alphabetical order not the latest one. Even though in both UI we have dropdown to select the LOV is not