You are absolutely misinformed and wrong about Pre-Open Era women's tennis. The best women players in the world consistently played the amateur grand slam events pre-Open era from the 1880's to 1968. The women who chose to turn professional and play exhibitions pre-1968 typically did this directly after retirement from grand slam amateur tennis.
Such wasn't always the case for men's tennis, where by the professional circuit often competed with the amateur circuit for recruiting best players, sometimes leaving the amateur grand slam tournaments pre-Open Era without the best players.
Historically-speaking, for women's tennis, there isn't much of a distinction between pre-Open Era and post-Open Era in terms of strength of grand slam field as there is for men's tennis...
Perhaps the pro/amateur thing was more applicable to the men than the women of the pro-Open era. However, there were still female pro players prior to 1968 that were not allowed to play the slams. Please note, however, that I made a general statement about pre-Open tennis that is regarded as true -- I did not make that particular statement specifically about pre-Open
Women's tennis.
I noticed that you really only addressed this one point. I had actually made several points. Refresher: The draw for the
Australian Championships and the early AO was considerably smaller (32 players vs 128 players). When Court won the AO in '73, the draw was larger but she was only required play 6 rounds (rather than a full 7 rounds at other slams).
Another point that I had made was the Australian Championships and the early AO was more of an Aussie tournament rather than a truly international one, as was the other slam events. Many top female players in the 60s and 70s rarely played Down Under. Top players of the time, such as Billie Jean, Nancy Richey, Rosie Casals, Ann Jones, and Francois Durr only played the Australian Championships/Open 2 or 3x during this period. (To put it another way, Richey skipped the "AO" 17x from '61 thru '78; Billie Jean skipped it 18x from '61 thru '81).
As I indicated previously, 46% of Margaret's 24 were from this subpar "AO" slam event. Margaret's 24 cannot compare to Steffi's 22.