I don't quite understand why it's still like this; it's probably the biggest reason why git tends to play poorly with a lot of filesystem tools (not just backups). If it'd been something like an SQLite database instead (just an example really), you wouldn't get so much unnecessary inode bloat.
At the same time Backblaze is a backup solution. The need to back up everything is sort of baked in there. They promise to be the third backup solution in a three layer strategy (backup directly connected, backup in home, backup external), and that third one is probably the single most important one of them all since it's the one you're going to be touching the least in an ideal scenario. They really can't be excluding any files whatsoever.
The cloud service exclusion is similarly bad, although much worse. Imagine getting hit by a cryptoworm. Your cloud storage tool is dutifully going to sync everything encrypted, junking up your entire storage across devices and because restoring old versions is both ass and near impossible at scale, you need an actual backup solution for that situation. Backblaze excluding files in those folders feels like a complete misunderstanding of what their purpose should be.