Always like the way he focuses on the first penetration moment, one of his best scenes is stunt cocking for cytheria squirt vehicle.
but i have to suspect, I've often heard stories from female pornstars that some guys need to inject their cocks to get hard. And famous guys are doing it. IF I had to speculate one guy of doing this it would be Mark Ashley. He's ALWAYS hard as a rock, walks into shot at 100%, still 100% after nutting, that kind of constantly ready to explode look that most don't get just from viagra. Sure some scenes with other stars you see this too, but this is every Mark Ashley scene for a decade. Combine that with his substance problem, and maybe he relied on doing that.
I definitely think if this was just natural ability he would be more renowned within the industry. but if everyone knows he has to do this maybe its why he's never been considered an all time great.