I would say that 6 seems to be the most likely situation here. Drawing up to the points at the southern end of the station before the northbound train arrives has happened before at that location, not necessarily the 6 buzzes, I just heard it this time around because of where I was sat on the train and could hear most noises from the cab, but knowing what the 6 buzzes mean it seems to be the most likely.
It does seem a bit weird to do that though, given that we were waiting there a couple of minutes, when we could have quite easily waited at the platform instead and started moving once the northbound train was visible, not necessarily at the other platform, but given that it takes a short amount of time for dispatch if it was when it was visible then by the time the points were reached the opposing train would likely have passed (being a mere passenger, I realise that there are probably operational reasons for this, but given that it was a warm day and having the doors open at Credition gave a nice and welcome breeze through the train, to be sealed back in seemed a bit odd!).