20420 is not very important, and likely wontfix.
22107 - same.
About 22107, at this point it is a documentation bug. this-command-keys and this-single-command-keys are equivalent (more info towards the end of that bug thread). But the documentaion still says that this-single-command-keys does not return prefix argument unlike this-command-keys. In fact, none of them return the prefix arg. So the docstring needs to be fixed.
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Kaushal Modi