Basically, the study has a fuckton of methodological problems that seriously undercut the quality of its findings, and even assuming its findings are correct, if you look closer at the data, it doesn't show what it claims to show regarding developer estimations, and the story of whether it speeds up or slows down developers is actually much more nuanced and precisely mirrors what the developers themselves say in the qualitative quote questionaire, and relatively closely mirrors what the more nuanced people will say here — that it helps with things you're less familiar with, that have scope creep, etc a lot more, but is less or even negatively useful for the opposite scenarios — even in the worst case setting.

Not to mention this is studying a highly specific and rare subset of developers, and they even admit it's a subset that isn't applicable to the whole.