Samantha, of Sewin Love came the closest to the correct answer. She wrote…
“I believe your pleats are pinned in the ‘wrong’ direction, looking at the pattern looks as though they should be folded in opposite direction. EG left to right rather than right to left?”
Remember, that pattern piece was placed on the fold, and I should have had a mirror image of the pleats when I opened it up. But I didn’t, when I took that photo, because I was busy not thinking about symmetry, and took the photo.
Later, before sewing down those pleats – thank goodness, no unpicking! – I realized the sides weren’t symmetrical, or each side folded towards the center. I re-pinned one side, then sewed down the pleats and basted across the top.
Dear Readers, did I present the puzzle adequately, so you had a fair chance at the answer? Be honest, please!!! I didn’t intentionally mean to trick anyone, and apologize if you’re feeling I did.
Thank you to all who wrote in a comment!