Mr VXR, Bill Beament, page-216

I don't know why those aiming for a quick profit would wait until the placement shares hit the market to start selling. In many and probably most cases, those who intend to sell would be better off doing it after the ex date of 15th June, but obviously selling the equivalent amount of those in their existing holding knowing they will be replaced. Those who have held those shares for more than a year would then qualify for the 50% capital gains discount.

The issue for many that have 1 year+ holdings is whether to sell before or after 30th June, depending on which tax year they want to have the gains in.

It's also probable that those who have held shares in VXR for less than a year, but still want to realise a quick profit, might wait until their existing holding has become a year old for the same reason.

There may not be a huge avalanche of selling on 19th July for these reasons.