Bullshitters work to convey an image of themselves one that's not true (in essence, lying) Like you just now in your post - Liars tell falsehoods to cover up facts, misdeeds, lack of knowledge and more. Donald does it all.
So for Donald he's the consummate conman - when he doesn't know something he makes it up. He does something wrong, he invents a story eg; "it was sarcasm to a reporter who asked a question".
That is not bullshit from him, it's a lie. He's a liar.