Agreed. I simply do not believe they practiced less.
I know a couple technical folks who are smoking good at their instruments, and basically said:
"Look, I spent time in <strong musical program> as an undergraduate. One group "has it"--they're the elite. I'm in the second group. I'm practicing my ass off, and I'm not deaf. I'm gaining some ground on the best in the second group, but it's REALLY slow as they're practicing their ass off, too. Maybe I can reach the bottom of the elite group after 4 years. Maybe."
"Or I can get a CS degree. And still play my instrument. And get amazing gigs simply because I am more than good enough and am always available when a cool gig comes up since I don't have to worry about money."