Your explanation makes a lot of sense, although it doesn't account for the stereotypical poorly-educated blues player, an archetype which Burnside was probably playing to.
Anyways, the Pat Boone thing was an allusion to the recording industry legend relating to Boone's cover of Fats Domino's "Ain't That A Shame." Boone, so the story goes, was a college-educated man and thus appalled at the terrible grammar in Domino's tune. He refused to sing it on those grounds. The suggestion that the lyrics be changed to "Isn't that a shame" was eventually coaxed out of him, at which point his handlers realized they had to talk him out of it. The song was eventually recorded as written, just... whiter. The story, however, has gone down in some of the more forgotten annals of music history.
