Well, Yuna got +1.29 GOE for her layback while Miki got +0.71 GOE for hers. So yea, relatively speaking, I think this makes sense. HOWEVER, I do agree with you that the comparisons don't make sense if we compare Yuna and Miki with Alissa. Alissa deserves like +5 for her layback if the judging system was more fair.
I don't Yuna's spins are that much better than Miki's though.