This is when you have 2 capacitors in series to make Ub+.. You can omit this central tap ..and use just end terminals and put to the bridge.
No pros and cons
The advantage of using a center-tapped secondary with a FWB and stacked reservoir in that way is it eliminates the need for voltage balancing resistors on the capacitors.
Not so much advantage, because resistors are so cheap.
I think is more job to make central tap during production of PT (more expensive) than put 2 resistors after.
Operation>
1.stop the winding,
2. fix the last turn
3. insert the insulation
4. make the tap
5. fix the return , to not unwind
6. proceed with the winding
7. terminate the tap with the extended wire at the end
8. lost of time
