It is unreasonable to assume you can delete a file from a sync app's cloud dashboard and not expect that the deletion would be synced to the device.
I get that OneDrive is a mediocre product that gets forced on end users, but so many people turn their brains off and just try to kill it with fire instead of thinking through their actions before making rash decisions. Deleting it from the OneDrive directory is marginally less rash, but again, people delete files without validating the original is where they thought it was.