"Developer time savings" (the proxy for output/speed they repeatedly reference) seems to be self-reported time saved by using AI? That makes "AI output accounts for 63% of the variation in developer time savings, suggesting that developers with higher AI output save more time" seem a little questionable, given prior research on how good (or bad, or inconsistent) we are at quantifying the time AI may have saved us on a task. A flip thing to read from that might be "developers who use AI a lot are likely to believe and report that it saves them time." That isn't a very interesting conclusion, though suggests one answer to "What are developers doing with that time?": maybe they aren't actually saving as much time as they think they are.

(presumably their analysis gets into more detail than just that one metric, I know their product measures other things less subject to bias in a survey, but it's hard to know what from this post)