Well - I have flogged off $15k worth stock many times before...

Well - I have flogged off $15k worth stock many times before when I have had an SPP entitlement in the past (mainly after the GFC), to arbitrage my position, but I would not do it if I was a long term holder with the SPP capped at $10m as this one is, with the current high SP. If the SP did rally like crazy for any reason, the cap could leave you with a shortfall. Also I doubt much of the selling could be retail seeking to arbitrage the offer, as the tax situation is that there will be a lot of CGT payable for most current retail holders - would be easier if there were capital losses that could be locked in.

So therefore I suspect that while some sellers might be recipients of the placement now selling or shorting, and some might be retail holders who bought at a higher price, most would be genuine sellers for whatever reason.