I feel that's a systemic problem with all consumer online-backup software: They often use the barest excuse to not back things up. At best, it's to show a fast progress bar to the average user, and at worst it's to quietly renege on the "unlimited" capacity they promised when they took your money. [1]

Trying to audit—let alone change—the finer details is a pain even for power users, and there's a non-zero risk the GUI is simply lying to everybody while undocumented rules override what you specified.

When I finally switched my default boot to Linux, I found many of those offerings didn't support it, so I wrote some systemd services around Restic + Backblaze B2. It's been a real breath of fresh air: I can tell what's going on, I can set my own snapshot retention rules, and it's an order of magnitude cheaper. [2]

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[1] Along the lines of "We have your My Documents. Oh, you didn't manually add My Videos or My Music for every user? Too bad." Or in some cases, certain big-file extensions are on the ignore list by default for no discernible reason.

[2] Currently a dollar or two a month for ~200gb. It doesn't change very much, and data verification jobs redownload the total amount once a month. I don't backn up anything I could get from elsewhere, like Steam games. Family videos are in the care of different relatives, but I'm looking into changing that.