Turning hockey player to figure skater makes no sense

I mean, they say 'we should have made her a single skater' at one point.

So, what exactly keeps her a 'double-skater' (or whatever the term is)? Why CAN'T they make her a single skater?

My point is, if they can turn a HOCKEY PLAYER into a FIGURE SKATER, wouldn't it be also feasible (and MUCH more so!) to turn a 'double skater' to a 'single skater', considering they're both basically similar things, and they're both figure skating?

The core of this whole thing is; it should be MUCH easier to turn a figure skater into another form of figure skater than a completely different skater into a figure skater, SHOULDN'T IT?!

The whole movie makes no sense, but especially this part is NOT explained.

WHY can they turn a hockey player into figure skater, but NOT a figure skater
(double) into figure skater (single)?

It makes no sense.