There have been a few studies that show that in certain circumstances this is the case. But doing a literature review will illustrate the bulk support the alternative hypothesis.

Ultimately, whatever the hype factor there is a large number of clever people putting their time and money into it for a reason.

I would read that study thoroughly.

It had a very specific caveat of "within existing codebases that the engineer was intimately familiar with."

In all other instances, it was not slower