It's not surprising. A tennis coach doesn't have to know tennis history to teach tennis technique and skills. But it is a shame.
This isn't uncommon. I have read stories of how famous baseball players are not familiar with baseball history.
I enjoy reading about the history of any top sport from chess, tennis, football, hockey, baseball, golf etc. It's nice to read about some of the fascinating things that has happened in that sport's history.
One negative about learning about tennis history is something I think a top former player expressed about Fred Perry and how they taught tennis in England. Apparently Fred Perry had an odd way of playing that was very wristy and was very hard to master. The tennis teachers in England tried to teach their players for years to play like Fred Perry and it really was too tough to learn. That was one of the explanations why a country that loves tennis like England couldn't produce a top caliber player of the level of Perry for years.