I go unmedicated now because it's a pain in the ass to get the prescription refilled (not the best, but whatever). But my experience was that the anxious procrastination mostly still happened when on the crank (I was a lot less absent-minded though which was something).
Additionally, the boost in dopamines rewards anything you happen to be doing, so it can lock you into your avoidant behavior that day once you start doing it.
Since Concerta is extended-release, this usually means that I have to start work early most days. If I take the medication too late in the day it’ll disturb my ability to get to sleep, and since the medication has mostly worn off by that time it’ll generally mean… browsing Reddit in bed until way later than I should be up.
(I should add that IME "body doubling"/"task shadowing" is somewhat effective, though not very consistently. It's also probably the hardest intervention to get, though maybe things like Focusmate https://www.focusmate.com/ might help with that nowadays.)
As a direct outcome it means I don't have bad thoughts and feelings sitting in the back of my mind when trying to do something else 24/7 so I'm generally more balanced. Indirectly, it was helped by actually getting stuff done and feeling less shit in general and not putting myself down as much for failing.