He wrote propaganda, beautiful brilliant propaganda. He wasn't an historian so the idea that he mangled something is a category error.
Oh, we know he was a sycophant, NS. I cite that Scottish farce as evidence. He made no effort to research any of the real story of the times, invented characters who simply did not exist in a bid to sooth the Stewart love of ancestry, Got Duncan's age and mode of death wrong, invented titles and places which didn't exist in Scotland - which itself didn't exist in its' present form - at that time; neglected to say that Macbeth wasn't immediately succeeded by Malcolm, couldn't remember Macbeth's wife's name, and invented the witches to blend in with James Stewart's obsession with 'Daemonologie'.
Apart from that, it was a reasonable effort.
I was belted in my second year after I presented a critique of it in my English class by a teacher who worshipped the brummie bard.
It's a hurt thing.