I'm not sure I understand... the UBEC in your link shows one set of wires without a connector (you'd connect your flight battery to those wires) and one set of wires with a servo connector on it.
(you'd plug that servo plug into your receiver, into any unused receiver port.)

what you're describing (but NOT what is shown in your picture) sounds like a dual / redundant battery regulator... meaning you would connect TWO separate flight battery packs, (the redundancy is if one battery pack dies)
in this case, you'd still only have ONE plug to plug into the receiver.