The quote is from the paper linked in the article: https://s3.amazonaws.com/real.stlouisfed.org/wp/2024/2024-02...

It's actually based on the results of three surveys conducted by two different parties. While surveys are subject to all kinds of biases and the gains are self-reported, their findings of 25% - 33% producitivity do match the gains shown by at least 3 other randomized studies, one of which was specifically about programming. Those studies are worth looking at as well.