I would agree. It is harder to get into "flow" mind-state when traditional or aid climbing. You need to stop to think when placing protection unless it's a very straightforward placement. In general, the more you run it out, the more time you can spend in "flow", although obviously there are potentially high consequences, and your mind will be screaming at you if you are, say, dangerously run out above a ledge, or if you placed protection absent-mindedly and now you are second-guessing how much you trust it. Free soloing is the extreme end of that: maximum flow potential, maximum consequences. Top roping is probably the best bang-for-your-buck in this regard: maximum flow potential, minimum consequences.

I've found acroyoga or other variants of partner acrobatics amongst the easiest activities to get into a flow state. I think it's because there is lot of novelty, a high-perception of risk (although is actually quite safe), and a high requirement for coordination. I would describe it as literally forcing you into the moment. Whereas when I run, practice yoga, lift weights etc., my mind is elsewhere.

This is super interesting! I might have to see what the AcroYoga scene is like around town.

This may sound a bit weird, but sports with "mandatory flow" really appeal to me. Snowboarding being the canonical example I use when I talk about this. I'm by no means as expert snowboarder, and when I'm doing it I have to be 100% in the moment. The sport has a great physical feedback loop for me: if I allow myself to be distracted, there is an immediate violent reminder (as I wipe out). Krav Maga has this too, although its more bursty (lose focus during a drill, accidental hits happen)

Thanks for the suggestion!