Wood chopper, I know that they are not interchangeble, and you are absolutley right!
I went to the Walmart in Cold Lake and wanted winchester CXP1 22-250 shells. With a dumb look the kid said, "we dont have any of those". I told him I was pretty sure he did. With a sigh he began looking at the .22 dynapoints and other 22 shells. I asked him if he found them. He said "No, we dont have them."
So I pointed and said "well how about those ones up there." He opened up the display case and he tried to give me the CXP1 223's. I shook my head and said, no the 22-250 shells next to the 223's. "Oh, those ones!"
HERE's YOUR SIGN.
One guy at our gun club wanted 12 gauge shells and the kid grabbed 20 gauge shells. He didn't look in the bag until he got home LOL.