Hope to give a convincing argument though its been a long time since I went SS!
Briefly then,
Firstly the formation of the bow wave:
The aerodynamic pressure at the leading edge (LE) is highest. The pressure and temperature reduce moving up stream ahead of the LE till a point is reached where they are akin to the free stream static values. Between this point and the LE speed of sound is higher than free stream numbers due compression. Also this high pressure and temp bubble is what deflects the airflow above and below the aerofoil. Result no bow wave
Consider a wing section at M=1.0, the disturbances i.e.Pressure waves are able to pass up stream only if the their propagation speed is higher than M 1.0 (which is not the case),The disturbances are contained. This results in a weak shock wave well ahead of the LE (in theory infinitely ahead).
Now the M Free Stream > 1.0, The pressure waves will bunch up and form the bow shock wave. It is the forward limit of influence of the wing.
As the aircraft continues to accelerate the bow shock wave attaches itself to the leading edge, this is called the detachment Mach No. which varies from M 1.41 to M 2.00 depending on the deflection angle.
Hence I would say that the answer is closer to M 1.3!
Can give further specific clarifications if you want them.