that was AFTER 4 days of running and if I recall around 400 laps. This is day 2 and Mercedes have yet to reach 30 laps total. They haven't finished a morning session and they haven't even put a tire on track during an afteroon session.
You're not seriously suggesting any driver at his first 1/2 hour of track exposure with a new team should be compared to the Alonso or fry your link depicts... do you? I hope you can see the difference in those situations.
Any driver no, Hamilton or any other top driver who drove a good car last year, should in my opinion be able to very quickly tell if the car has more or less downforce than he is use to.