It would be pretty normal to have the float "ready to go" in the background, with the major work being done some time ago (have worked in the space) - a partial float, in reality. That's what advisers are paid (lots) for - the models (several scenarios) would be updated regularly and instos kept schmoozed.
As for the rationale attributed to GyG - that sounds pretty dodgy; maybe more about 'market sentiment' . The best proxy for appetite for VA stock is of course Qantas, and I am surprised to see that their recovery from the bottom last year has stalled a bit.
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If there is no apparent local prompt for the partial divestiture by Bain, it might be exogenous - a foreign cornerstone investor indicating that they are ready to go.