Some people say yes, others say no. Certainly sorting out bad ones can help. I have tried sorting into weight bands and also washing / lubing pellets. For my standard of shooting I found it made no difference and I had better things to do with my time. But if you are truly aiming for the highest standard then I can see that it could have a slight effect in addition to the psychological effect of knowing that you have done all you can to guarantee your own performance.
Try it and see.
Cheers, Phil