"That said, I do find myself wondering why the hell they are using all these non-winter sportsmen and women to present, when we have so many other more knowledgeable people who could do the job."
I wonder if we do though (or at least, do the BBC")? Winter sports are a minority interest in this country, so first we have to find people who compete at a high level, or have some other involvement. Then you need to find one's who are willing to commentate on tv and can be trusted to do so competently. Then you need to find one's who are not contracted to do it for another broadcaster, or who are willing to do it for the price the BBC are able to pay.
Ed Leigh and Graham Bell pretty much cover the BBC's usual winter sports output so I wouldn't be surprised if they struggle to find suitable available talent for a four yearly event like this, hence picking other commentators and hoping they have enough time to read up on the sport they are asked to commentate on.