This, I believe, is a pic of a Metro 1275 engine.
So the inlet ports of 1 and 2 are siamesed as are 3 and 4 , but the exhaust ports of 2 and 3 are siamesed, with 1 and 4 being not siamesed to anything.
So maybe this is where the confusion has arisen.
I wonder if he has an LCB. He ought to...