Does it matter that he's in a Seaplane, as he can potentially have been taking off or landing....?
Apparently it does.
Some float planes are permitted to be in the helicopter lanes west of the bridge.
He certainly wasn't landing because he turned up on the Bankstown frequency a short while later, but I suppose he may well have been taking off. I guess he still would have needed a clearance.
Thanks for the replies. Might have a go at getting a clearance at 1500 next time I am playing spot-Joolia at Kirribili House.