What would be the difference between a new bike with no plate and a 2nd hand with the plate legally removed.?
Answer .... Both have no plates.
See my point
In both cases, with the correct documents, both bike can be legally registered in your name IMO.

with the case of buying a 2nd hand bike, I would before I pay is to visit the local Traffic Police from the area the bike is plated to confirm the bike can be de-registered.?
And ask what is needed to register the motorbike in your name?

I did advise you some time back you have a guy on your doorstep (bikerDoc) who has in the past registered bikes from other province and from a foreign owner who has been successfully in registering the bike in his name?
He may have time to help/advise you on this matter.
No harm in asking.