Perhaps, but keep in mind that a broker just facilitates the...

Perhaps, but keep in mind that a broker just facilitates the request of their client. The buying for CBA doesn't mean that CBA are placing those orders, it's the retail clients obviously. That's the issue with the broker data, it doesn't really provide all that much information at all in relation to who is actually doing the buying and selling, just the broker that is facilitating it. Who knows though, there could be some complicated answer to it or it could simply be a muppet who has no idea how to minimise market impact cost when trading large orders.