Yep. Makes perfect sense to me. Trying to end feed an auger (rotor) is the least efficient way to feed it. But it's not so much the half diameter that does it as it is pushing the material into the end instead of the side.
I had 2 2188's and on my 3rd 2388. The 21's were a good machine,no real problems. The rotary screen and air cleaner intake on them was better than the 23. I could get days out of a filter but the 2388 needs to be cleaned at least once a day.3 speed rotor gearbox was a good improvement, all else is much the same.