Sorry you asked how to replicate it so I just gave you the method quickly for the Windows 10 aspect of the thread
The problem with disabling the history is with the productivity benefits the clipboard history gives to the users. After using the Windows one for around 4 years now, I can’t imagine not having it. Just typing out commands into PowerShell from a data dump is so much easier with the history as there’s less flicking between monitors and open programs.
Like Robster and WinBW have said, I think it’s the wording of it that causes the misconception. “Clear Clipboard” to me would mean deleting the entry so it’s no longer an item in the clipboard history, especially for Windows and Mac which has it built into the OS - not separate apps like SwiftKey or flycut are. The history functionality in these operating systems have been around long enough for this to be the default assumption for myself and the others that have raised it here and on GitHub. Perhaps adding a warning alongside the option that it cannot clear the history would at least warn users that use histories rather than them believing it to be a bug or issue with their setup?
It’s already being tracked in GitHub so hopefully once the browsers support it after the experimental stage it can be possible 
(Issue #557)
In terms of the SwiftKey clipboard history, it can be turned off under Rich Input > Clipboard although this may not be a viable solution for everybody, I don’t know if it would be possible or feasible to clear third party app histories
