The reason is simple.
Everyone
knows mid drive is better indoors and usually a fair bit worse outdoors. Which with stock chairs, very true. But the reason for that is that every last rear drive chair available is nose heavy and is a foot too long!
Where you
universally have swing away footrests as stock, on rear drive, that make it long! Since they must clear the casters. Your legs / feet then end up stuck out ahead. And hit every doorframe, while over loading the castors so it steers like crap... My BM3/2 chairs and now a modified Salsa chair that I just purchased has a centre foorplate added. Allowing the seat to go back with your body mass. So the whole chair ends up shorter, and with a centre plate partly between the casters also easier in confined spaces indoors, and no longer hits every door frame as you turn. And it steers better because now your mass is over the rear wheels, not sat on the castors!
But they dont seem to get it. But a hacsaw, drill, and a
can fix this on many chairs. Which is why I ordered a Salsa. And then reconfigured it. But this is the reason they are vanishing from the market.
(The C350 is too long between the casters and the drive wheels to do this. So is always nose heavy. And only has 60Ah batteries?)