I think this has happened on all my LR's with climate control - I believe the system directs heat to the windscreen initially on cold mornings and once warmed up then directs it everywhere sensors request it. You can override it but this will reduce efficiency clearing windows

The auxiliary heater speeds things up a bit

From my handbook and might help to increase efficiency and speed up process -

Quote:

Note: In low temperatures it is advisable to
close the centre face level vent and direct air
flow from the outer face level vents towards the
side windows. This will help to keep the
windows clear of ice.