Funny thing about headspace is it can lead you in the wrong direction. Case in point: Case too short, gets pushed forward in the chamber to the shoulder area, primer won't ignite so you blame it on the primer. Throw out a batch of "good" primers that you think are junk and try another brand that's "better"? (just had one happen yesterday) All the other 40 rounds fired OK. Or, you find that the primer wasn't seated all the way down like the rest of the batch. :-[
You still condemned that brand of primers. Same with powder. Work it till you can't get anymore out of it. So and so says this is a better powder so I'll go with that. You never found out the true potential of the first brand. Too busy jumping around. ::)
Same with resizing your brass. If it feels good to you, do it.
If someone else does it a different way and you like the results, go for it and see how it works for you. Never stop learning. If you stop learning, you're not doing anything. ;D