OK. well I should have said "equivalent in performance ability to . . . "
But if a musician is unable to play arpeggios accurately they are going to have a lot of trouble with, for instance, Iron Legs which I know for a fact Greg can play very well.

Oh, and the old prejudice about "proper trad musicians don't sightread" You astonish me, Greg. Sightreading is only a skill which anyone can acquire and jolly useful and timesaving it is too.