I found it went up if I did the test after doing some of the exercises. (30 something) but if I do it at the start its consistently low at around 19-20

Would agree yoga is tough. My legs arent very flexible so I really feel the pull on the the ones involving touching toes etc. Which I guess is good.

How does the jogging do its scoring?  My first jog I did 104% then 54% then 44% and I dont think I did any different between each run.

I think its a combination of how fast your pace is and how regular it stays. The person you follow speeds up a little if you go fast, so to a point if you go fast from the start and make sure you dont overtake him/her and keep the pace/your distance you get a good score?

I think they do the jogging from the point of view that people get the best out of it if they push themselves to keep a set pace and not just walk it or something. If you slow down too much/too often they probably score it as a sign of unfitness or something?

If you overtake him/her when the dog is in front you get an alternate route too

Ive never overtaken them.  I went hell for leather and got 75% :-/  
So possibly  a consistent pace rather than a specific pace.  That makes sense.  Ive seen the alternate route but I wasnt running at the time