Is one really good technique enough?

I just had a thought about how a game in sparring could be. I recalled the techniques learnt and there are so many techniques out there but sometimes it just takes a few good ones to win the games. In the national training team it seems, each has its own specialization or perhaps all are trained in the same technique. It may be good to be really good at one technique but in the game of sparring it is better to have some form of variation because it is often the surprise technique that will make a difference.