AnOctorokForDinner
Talk Tennis Guru
Okay, I found something more reliable. I've looked at both Open Era history and overall Tennis history and compiled a list of all the players that have held Wimbledon and French Open at the same time. As we know, there are two ways of doing that:
1. Channel Slam: Win the FO-W double in the same calendar year, the way Federer did in 2009.
2. Non-Channel Slam: Win the W-FO double, by winning Wimbledon in one calendar year and then the French Open in the next calendar year, the way Djokovic did in 2015-2016.
Here are the results:
In the Open Era:
Channel Slam: 7
Non-Channel Slam: 7
In the pre-Open Era:
Channel Slam: 8
Non-Channel Slam: 5
Overall:
Channel Slam: 15
Non-Channel Slam: 12
So, over the course of Tennis history, it looks like holding both Wimbledon and French Open at the same time, the way Djokovic has, has happened less often than the Channel Slam. This is a way bigger sample size, and we don't have any inconsistencies in terms of prestige of Slams and participation the way we had with the Australian Open.
No inference may be drawn from pre-Open era results regarding modern tennis.