There is some group off jj2ers who don't like to play other gamemodes because they're not good at it. sometimes they are not good at jj2 at all, then they keep losing.. I think for them playing tests is a lot more fun since you can't really lose in them.. only win. only some part to get trough.

But, to get trough, you actually need some skills after all to get trough, what i think it's the reason why most tests which are hosted today are pretty easy.
(those people make those tests on their own playerlevel i guess..)

and about the thread question. i think it does a little, a very little job on your skills.. however. that's only one ability: movement. thinks like gameplay wise thinking aren't really included. nor getting trained at tests. which are still 50% ability you need to be "skilled"