Nope, Fedor also did it. I think the technique is grounded in sambo. Sambo inclues ground and pound and so it has grappling mapped out to incorporate it. Unlike less realistic wrestling and BJJ.
Obviously wrestlers and BJJ guys train GNP for fights but they don't do it the way guys like Fedor and Khabib do. It's not as developed and the martial arts aren't literally designed around it. Guys just do it in training as an afterthought. Sambo is designed as a martial art around it.
If you look at Pankration art and statues from thousands of years ago, it's evident that pankration fighters had grappling technique mapped out to incorporate ground and pound too. That's understandable -- they practiced MMA for thousands of years. So, they were still a bit ahead of technique from where we are now.
This is also proof that the sport still has plenty of room to evolve. Those who think it hasn't evolved since 2005 and won't evolve after 2018 are fools.