Basically, what they say is that there was a period in the 20s and 30s when retired (and in some cases married) Takarasiennes returned to perform with the Revue. The term they use is 復帰 (fukki), which can be translated as (1) "return; comeback" or (2) "reinstatement".
This site states that Wakana Kimiko retired in 1925, and in 1926 Yukino Fujiko, Tatsumi Sumiko, Suminoe Kishiko, and Ariake Tsukiko, and that they then "fukki"ed in 1927, for three years. They say that this is probably from something they found in Ikeda Bunko Library (which apparently has an impressive collection on Takarazuka).
This one quotes directly from Kageki issues in 1927 when they talk about Suminoe Kishiko's return in 1927. They also mention that countless seito left and returned around 1930-31. Apparently Kobayashi Ichizou had created the 国民座 (Kokuminza), The People's Theater, and a lot of seito left Takarazuka to join it. When it went under, they returned to Takarazuka.
I find that really interesting. The 90th anniversary book lists Suminoe Kishiko as retiring in '26, but Yukino Fujiko as retiring in '34 and Wakana Kimiko as retiring in '31. Revisionist history? Garbled fan research? Or just too many versions of the story?