George III was not as willing to tolerate so much bloodshed as was Lincoln. He certainly could have won had he been willing to kill so many people as he could have done.
When it comes to making crap up who better than you would know?
Who better to recognize made up crap than myself? I'm sure there are others out there, but I am pretty good at recognizing made up crap. The secret is in researching a subject until you actually know something about it.
So then what you're saying is that Lincoln would do what it took and accept the sacrifices necessary to win the war that the rebels forced upon him but that George IV would not. That would be an indication of exctly how much each man valued their cause.
Do you suppose that George III would have thrown in the towel had he not had a major war with the French at the same time.