Also ADHD here. I find smoking a little helps significantly with turning off the distractions of Slack, email, reading interesting docs that cross my path. It's much easier to sit down, crank out a coding task, or jump into a deep debugging session.
Not something I do often (or even occasionally), but I definitely don't think it's nonsense.
Undiagnosed but suspected ADHD here. With a bit of THC and some electronic music I can bang code out for hours completely in the zone. It's like I build a great mental model on what I'm working on and become very immersed in it. I can't do it too often as managers need their meetings and updates but it's the most "zen" I ever feel.
In my experience, being in any alternative state of mind, whether from caffeine or moderate amounts of alcohol, or even something not substance related- after working out, after a good night's sleep, after a bad night's sleep (the sweet spot is four hours), there is a sensation of productivity benefit, but I hesitate to claim there is actually productivity in every case. I think these altered states of mind help make it emotionally easier to cope with whatever the underlying cause is- possibly ADHD, possibly some variety of anxiety- and thus make it feel easier to work or engage in other difficult tasks. But cognitively? That's a whole different story.
Not something I do often (or even occasionally), but I definitely don't think it's nonsense.