Bart B, Since Sierra has there own way of doing things to test their bullets why would anyone want to call them and ask about weight cases. If you think it's import to back up what you said why don't you E-Mail them ask question them post their answer.
I load to what's important to me as to the accuracy in my rifles and if it takes weight case I'll do it.
Here is Record F-Class shooter that sorts case
Here is another record hold that weight sorts that's not F-Class
What you should do is get on some site with match shooters like 6br or benchrest and ask those guys how they prep brass.