The French was meaningless before 1979….. before then it never had all the top players entered. Example, Laver in the early 70s played the Italian which was on after the French and demolished the French winner of that year Kodes. Laver didn’t bother with the French, he had WCT events with bigger prize money on offer during the same weeks.
The world number 1 of 1974-78 didn’t bother playing the French, even Borg didn’t bother playing it in 1977, it only became prestigious from 1979 when basically everyone played it. And the same is true of the women’s event…..1976, 77, 78, where were Evert and Navratilova and Goolagong? They didn’t bother playing the French. It had basically no cache.
I am not here to argue but to educate. Think whatever you want, but tennis in the 1970s was all about Wimbledon, the US open and prize money. For example, in 1970 and 71, Laver doesn’t win any slams but leads the prize money lists. That’s why he was considered number 1 by most for that time.