I think it’s a decrease of receptors or an increase of re-uptake. But yes, there have been results pointing in that direction, but as far as I’m aware this is not as clear as that. Who does it affect? Is it seen with abusers or with users of (generally much lower dosed) meds? How much? How does this compare to the dopamine deficiency we see without treatment? Etc. But if you have a good and recent source, I’d love to read it.

Cite please?

You're misunderstanding the action of the medication and the defect in the brain of adhd. Adhd is an abnormal density of dopamine transporter.

Receptor density might increase, but that's negligible in the system compared to the starting density of transporters at therapeutic doses.