In some ways it’s just a technical difference (syncing vs backup “snapshots”). It’s totally true that if you throw away a file out of iCloud or OneDrive, there is (I believe) a window of opportunity to get it back out of the cloud.
But I also don’t think either let you get back a version from 3 weeks ago, for example, which is where versioned backups like Time Machine and File History come in.
Honestly, it is good to have both enabled for various reasons, not the least of which is just having a copy of your files offsite.
Say what, now? I have yet to run into a Linux site that casually lists what all hardware is compatible before you start trying to install stuff. The same with Windows, for that matter, although knowing Microsoft there may be a database squirreled away somewhere.