u r more or less correct there, what u are talking about is also known as scavenging. Your design would work well as the firing order is 1342, so with your design the pulse from 1 draws the pulse from 3 in the first Y then the pulse from 4 will draw the pulse from 2 in the 2nd Y, the pulse from 1&3 then draws the pulse from 4&2 into the main pipe,
this is why V6 or V8 with a T intersection can run smooth without increased backpressure in one bank of cyls,
hope that makes sense.