I'd go one step further and add that you may need to prove your Entitlement to your broker. Telling them that you have Entitlements may not be sufficient. Proving your Entitlement might not be possible until on/after the Opening Offer Date (31 Aug).
My working thesis for why some shareholders have early access to trading the Entitlements might come down to how their broker manages their client relationship (for want of a better phrase). I suspect that some brokers might be prepared (or have the back-office tech info systems) to allow their clients to trade the Entitlements without Computershare actually having released/confirmed the Entitlement details for any shareholders yet (due on Opening Date - 31/08). The theory runs along the lines that, since the client is CHESS sponsored, their broker should be able to work out how many cum-rights POS holdings their client has before the Entitlements have actually been issued. And on the strength of that, the broker allows their client to trade the rights, in the knowledge that they will be issued to their client and available when settlement is due. And since all the rights being traded are on a deferred settlement basis, money/rights won't be trading hands until after 05/09 (i.e. when rights trading stops).
(20min delay)