IMO, the reps should only be strict until you get to about 80%. Afterwards I believe some cheat (low back movement) is perfectly acceptable. Rows are a fantastic core exercise in addition to upper back. For those of us that don't do low back work (outside of deadlifts) some cheater rows are great. I'm not talking like standing all the way up into a shrug.. I'm just talking about a little english to get the weight moving and really pulling into your midsection. Not to mention the secondary posterior chain activation.