cjg...
Technically....you should actually perform an operational check of each separate affected DC system prior to any paralleling checks after replacing a DCU...
The M&O was never really clear on this...and if memory is correct it was actually dealt with in Vendor's manuals on DCU.
But straight up... yes...you need to parallel the DCU's if changed out...even if swapped...as the #1 and #2 systems are independent of each other....
w1