To have this thing you’re not supposed to need to worry about affect whether your files got backed up is exactly the problem here. The goal is to back up your files, whether they’re in the cloud or not.
I sympathize with Backblaze’s problem with their file change monitor, but then they should considee implementing connectors for OneDrive, Dropbox, etc. and back up files directly from the cloud.
I think backing up the materialized files is appropriate. That’s what they (used to) promise.
Or maybe just do what they do now, but WARN about that in HUGE RED LETTERS, in the website and the app, instead of burying it in an update note like weasels!