I've causally/intermittently followed this thread. There appears to be a problem of definitions and applicability.Is there a page of definitions for jessie, jessie-updates, stretch, stretch-updates, stretch-backports, stretch-backports-sloppy, buster, buster-updates, buster-backports, bullseye, sid, experimental, "fastpace/not ready", "Fast Track repo", etc.
I use only "stable" so doesn't seem to affect me.