Manufacturing ease is my guess. Why have another whole cylinder assembly and piston when you can have them both the same. Probably got a break from Mahle on them since more quantity. The air filters are different on the 365 and 372 so I can see a harder choice for them.
The HD filters on the 372 mainly is a US thing, and not universal. I would take a "low top" any day over here, but cutting conditions vary.
They soon discovered that the difference in the transfer covers were too easy to fix, so the price of the 365XT/2166 went up after a (short) while - but there still is a difference. If it is worth the difference to not have to fix the transfers is up to the costumer. The 365XT/2166 is the only saw model I know of that is this easy to upgrade though.