Sport Riding Techniques, by Nick Ienatsch, if you can find a copy.
Written by a guy who's an AMA top 3 250GP rider, a magazine editor, and, ironically enough, a class instructor, too.
No flashy, outdated video. Just hard text, which you can go back to for brush ups.
https://www.amazon.com/Sport-Riding-Techniques-Develop-Confidence/dp/1893618072
Good for you for trying to improve. A while ago I read this book that really taught me a lot. It's worth a read in my opinion, really good advice for real life as well as track riding.
I don't know if Nick is the guy behind the u/champschool or not but his book deserves a plug.
https://www.amazon.com/Sport-Riding-Techniques-Develop-Confidence/dp/1893618072
I was recently loaned this book
https://www.amazon.com/Sport-Riding-Techniques-Develop-Confidence/dp/1893618072
The skills it gets you working on are amazing and it'll make him a safer rider.
You wouldn't be paying money, but you would be sacrificing a learning experience. A small bike a like a 250, 300, 500, or twin 650 allow you to learn the basics of braking, throttle control, leaning, body position, and two-up riding with a large margin of error. Even on their limits in power, grip, and braking a "practice bike" will inspire more confidence and develop solid habits. Additionally it's your starter bike so you aren't as concerned if you drop it. If you worry about dropping your dream bike, you will ride much much more slowly. Will you be bored on a starter bike? On long straights yeah, as squids would say they have "no balls". But you won't be scared of your own bike which is how most supersports and liter superbikes are ridden on brakes and turning.
Of course just having a starter bike wont let you learn some techniques. Some you have to learn from an instructor. Twist of the wrist is ok place to start, but the techniques are becoming antiquated. Here is a more modern book with techniques applicable to modern riding.
On a R6 you can learn those things very slowly but at the price of riding the bike to a quarter of it's capabilities. You have to ride a par-quality sporty bike to appreciate the features of a true sportsbike.
The R6 has one of the highest rev limits in the i4 600 class. You will briefly be able to use this amazing power on a long empty straight. Other times you'll probably throw on an expensive exhaust just to feel something at the lower revs. Whereas it was meant to give maximum drive coming out of track corners.
The dual disc brakes will offer enormous of amounts of stopping power, but are they beginner friendly? The inherent instability of the front end intended to give the R6 a quick change of direction, you won't be shredding corners. The instability of the front will sap a lot of confidence when you're riding in a parking lot.
The ride height everyone is warning you about? Easy fix? Just lower the height. You would be robbing the R6 of it's advantage as a middleweight supersports by removing weight from the front. It sports a side exhaust and marketed as "mass-centralized" give the R6 it's amazing track capabilities as a mass produced sportbike.
If you don't really care about what I think you would be sacrificing by skipping a starter bike then go ahead. It is a pretty bike. You don't have to ride it the way it was designed to be ridden.
EDIT: also the only way to really learn the limits of the bike is on the track. You would ride an amazing sportbike, but because streets aren't tracks you'll only use 50% of it. Might as well get a street bike with 50% of the R6 potential and get a R6 purely for track. If it's your dream bike you'll wanna specialize in riding it no?
Also check out Nick Ienatsch Sport Riding Techiniques and his similar article from Motorcyclist in 1991 The Pace.
First, fear of your tire is very founded. I see so many people, particularly on budget motorcycles running the most gawdawful, mismatched, chinese tires imaginable. So good tires will help a lot.
Second, the best book, bar none, 10:1 over any other book out there is "Sport Riding Techniques" by Nick Ienatsch.