"CCC no longer excludes 1Password by default."
What the fork were they thinking?!
Update: OK, looks like they did this briefly in 5.1.18 and, even though their language is sadly unclear, it was the the 1Password app rather than the 1Password credentials that were not being backed up. That link lists all the files not backed up, though as of today it's not been corrected for 5.1.19.
So I still have chest pain, but not a heart attack.