I think there was one version of Al Tyll’s book that had an “attempt ratio” or some such metric. There are far too many variables to venture a number. Assuming decent coaching and decent equipment, I would tell them not to fret. Practice makes perfect and they’ll get the hang of that trick before long. If others can do it, they can too. That’s why I emphasize studying video of others. Don’t sweat it. Have fun. If you ain’t falling you ain’t trying.
Then again, I still can’t do a wrap-in TO consistently. I threw out the attempt ratio a long time ago.