I've long wished for more studies like this. So it's good to see.

This one does miss some important variables:

1. Dose-dependent effects

2. Naive vs experienced users of a drug

3. Novel vs familiar task

Though the authors spend a lot of time showing these stimulants reduce work efficiency, their central finding seems to be: "There was no significant effect of drug on performance"

https://www.science.org/doi/10.1126/sciadv.add4165