I learned how to clutch and shift in an old 1930 Chevrolet. It was up on bricks, being restored.
I was about 12 years old at the time, and when I turned 15 and first drove on the road (1975 Ford Escort) it was easy to master the technique of shifting. Admittedly I'd ridden motorcycles a bit by then, but I still believe that old Chev taught me the basics, even though its wheels weren't actually touching the ground.
Having said that, it takes perhaps 5+ years on the road in traffic before you can consider yourself an experienced road driver. Regardless of how much practice you've had, how many miles you've done, or how skilled you appear to be, until your mental approach to driving matures you aren't really there yet.
Any practice is helpful, even LFS, but there's a lot more going on in real life that will affect your ability to drive well.
*sorry for the slightly O/T post