Does the authour believe the story of the sweetheart of the song Tra Bong? Cite evidence supporting your answer.

No, the author does not believe the story.

"This one keeps returning to me. I heard it from Rat Kiley, who swore up and down to its truth, although in the end, I'll admit, that doesn't amount to much of a warranty."

Nope, author never believes the story . . . duhhhhhhhhhhhhhhhhhh.