[DonRotolo]

A parallel connection offers lower resistance to flow, meaning higher potential flow rates with less pressure drop in the lines. Although the regulator's single connection is a restriction, unlike hydraulics the gas (air) is sompressible and so the restriction is a point resistance rather than a system resistance. So, you do gain a small advantage in flow rate and available pressure with parallel 'plumbing', at the expense of weight and a little complexity.

To illustrate the restriction issue:

In water pipes, you can run 50 feet of 1" pipe, a foot of 1/2" pipe, and another 50 feet of 1" pipe. The maximum flow is dictated entirely* by the 1/2" pipe.

With Air, using the same setup, the flow is more dictated by overall air velocity, the 1/2" pipe is not much of a restriction at all. (Higher velocities cause more drag in the pipe, which restricts flow).

Don

*the effects of drag in such a case is negligible.