I would think that the reason for the centrifugal pump is to eliminate the impeller changing on the Onan.
The impellers don't last very long in most cases. That's my experience also.
I have a March pump which I will install when I run out of stock of impellers, but I will completely bypass the impeller pump and feed directly into the heat exchanger.
I first saw the March pump on Amelit with the previous owner.
Elyse SM437 .... soon to be reunited