The latest CIA document dump also provides more background on how Abu Zubaydah got subjected to extended sleep deprivation long before it was approved. PDF page 113-114 explains:

After consulting with the NSC and DOJ, CTC[redacted] originally approved 24-48 hours of sleep deprivation.

In April 2002 CTC[redacted] learned that due to a misunderstanding, that time frame had been exceeded.

However, CTC[redacted] advised that since the process did not have adverse medical effects or result in hallucinations (thereby disrupting profoundly Abu Zubaydah’s senses or personality) it was within legal parameters.

There a number of important points about this.

First, note the timing: April. When AZ was still recovering from bullet wounds and surgery.

This was also the same time period when (oops!) Binyam Mohamed was being subjected to extended sleep deprivation, presumably pursuant to the same kind of “misunderstanding.”

But also note the language. The “profoundly disrupt the senses or personality” is the language on severe mental suffering that John Yoo gave John Rizzo on July 13, 2002, which Jonathan Fredman sent to the torturers as their guideline on torture. It seems likely, then, that this (oops!) sleep deprivation was the “incident” that CIA was so concerned about as they were writing the Bybee Memos.