No.
A "Y" would be 2 into 1 for a single exhaust.

If you have 2 separate exhaust tubes, one for each side it's called dual exhaust.
If you add a tube connecting the two, it effectively doubles the available area for the gases to go when one valve on one side or the other opens reducing back pressure.

It does not seem like it would be much, but it is.

High performance race cars once used a double crossover tube in an "X" pattern to make the flow as smooth as possible at extremely high Rpm's.