at point of contact.
So, if two heads or head and knee collide with greater impact due to a roid'd body applying more force than an unroid'd body, then the negative effect of the collision will be greater. More CTE issues / concussions. A harder pounding to the head = increased likely hood of head trauma, or greater head trauma than if the overall body mass / strength had not be jacked up by roids. The direct link here is the ability to apply more force due to the increased strength and muscle mass + speed from roids. Without roids all of these would be lower and collisions would be less threatening on an overall basis, hense not as many concussions in the pre-steroid era of sports.
I wasn't looking from the angle you mentioned of chemical/nerve reactions based on use. But, to your point, if there is a higher CTE rate in those that use because of the nerve reactions in the brain... again remove steroids and that rate drops.
Based on the new insight, for me that you shared, if you remove steroids then we likely remove 2 very plausible causes of increase CTE. Reduced strength/collision impact and reduce nerve issues you brought up. Two wins should reduce concussion rates even more than I'd previously thought.
So, it's a win-win for those actually playing the game? Yes, the fans are the loser her as the game likely loses some of its luster due to a decrease in athletic performance without all the enhancers, but that's a complete guess. You never know until you get there.