This has been going on my entire career, starting in at least 1996 or so. Maybe SanDisk was an exception? People have been complaining about this for a very long time so I don’t think it’s quite right to call it Shrinkflation.
But, maybe I’ve been conditioned into complacency. I do agree, manufacturers should have to post usable space. I don’t see this changing though.
Edit: Removed note about 1,000,000,000 bytes. The article isn’t specifically about that, but I’m not convinced that’s ever been the only factor.