That's not true at all. Laver developed that big topspin backhand as a junior. That was thanks to his original coach, Charlie Hollis, who was a huge advocate of topspin as an aggressive shot off both wings and insisted that Laver learned how to hit it. In turn, Laver was very heavily influenced by Lew Hoad who hit topspin off both sides.
What Laver developed, as he got older, was the physical strength to control hitting such aggressive spin off the backhand side continually. It's one thing to hit it occasionally but it takes a lot of wrist strength and physical strength to hit it repeatedly with a wooden racquet and while using a Continental grip. That's why Hoad was such a freak - he was able to do it well enough from the age of 18 to be one of the world's best.
Nice info AndrewD. Charlie had all his guys doing the fishing line with the weight on the end , broomstick roll-up, roll-down technique. My coach had us doing it too but all I got was sore wrists!(wrong biometrics, bodytype).
Hoadie and Laver built their arms like steel cables!
Even in 1983 ,when I last saw him, his right arm was bigger than his right.
Ditto for Laver with his left!
When Macca went away for 6 months to Hopman's that was unheard of.
Normally the end of your career...it kickstarted his!