Ah yes, my visual memory was correct, but the reasoning for the shape was incorrect.

AFAIK we don't actually know that the Bent Pyramid was a design flaw with a course correction in the middle. We only think that because it's the only one with a slope that changes in the middle, but there were few pyramids before that one: before the Bent Pyramid was the Meidum one that also had a steep slope, and before that was Djoser's step pyramid, which was the very first one. And Meidum was a step pyramid too before the sloped casing was added in the last phase. We don't actually know that they planned for a very tall one then gave up, and what they were experimenting.