Only three players completed boxed set - Doris Hart, Margaret Court and Martina Navratilova.
Honorable mention: If player wins all 4 majors, olympic gold and year-end tournament in same year, it’s called super slam. In 1988, Steffi Graf achived a non-calendar year super slam. In 2021, Diede de Groot achived this feat in women’s wheelchair singles.
True. Maybe one of those stats folks will tell us about men who have won doubles and mixed doubles at all four slams in the same year.