I remember one business class anecdote, where the conclusion of changing workplace conditions (light, music, etc. both ways) was that productivity studies increase productivity ...

It's Hawthorne effect

https://en.wikipedia.org/wiki/Hawthorne_effect

Related to it we have novelty effect and bunch of other psychological effects that are hard to isolate in human science. In this sector, a lot of studies cannot be repeated.

Only if you do bad science experiments without a control group, otherwise you'd see the control group productivity boost as they'd also be under the same scrutiny. I didn't read the study methodology, so I'm not comparing to that, only responding to your comment in isolation.