Rowing And Pullups With Short Arms

Ive never felt rows or pullups in my back ever and it never seems to grow. For the last few months ive been rowing and doing my chinups with those plastic grips you tie around a bar or pullup bar and they dangle down for you to grip.

I can now barbell row with great mind muscle connection and ive taken my pullups from 2 to 12 at 225lbs. My shirt feels much tighter around my back too. Can anyone explain what this could be about? I got the tip from a bodybuilder at the gym before i moved after asking him for barbell rowing advice. Hes got trex arms too and said I should give his grips a try.

Does arm length make a huge difference on back exercises?