Dual Breather Lines

[Multimotor]

1976 T337G

Why does the rear engine have dual breather lines (the normal one at the front of the engine, and one from the oil standpipe), but the front engine has only one?

It's a rather cumbersome arrangement that has a T in the line between the two outputs that sends one drain line to the air/oil separator. Seems they'd work against each other.