Your explanation makes sense and I understand it!
I did see that page in the manual but I found it confusing, I wasn't sure why they were showing Y splitters at first.
I just read on page 9 "If the pre/pro does not have a spare set of line level outputs, a 1M-2F Y-adapter may be used on each pre/pro output in order to split the signal and allow connection to both the loudspeaker amplifier and the subwoofer amplifier. "
The Saga+ pre does have two PAIR of outputs.
Now the question is, which method is better or will sound better!