if the r22 was suffering from a lead lag stress, then you would have to imagine that the same egg shape wear of the journals would appear at the coning hinges in addition to the teetering hinge (and since Lu didn't mention observing this I assume it was not the case).
as for retreating blade stall, Lu, as forward airspeed increases, the local airspeed experienced at the retreating blade decreases. examining the lift equation, to compensate, the angle of attack must increase to equalize lift on both halves of the disk. At some high forward airspeed, the flapping will cause the angle of attack to exceed the critical angle. I would hesitate to use the word "inflow" because this is most often a term relating to transverse flow, which is another subject. The actual speed at which retreating blade stall occurs depends on the helicopter and pitch setting. the r22 Vne of 102 kias at low density altitudes is probably in the vicinity of this speed. I've been told, however, that it was difficult to demonstrate the onset of retreating blade stall during the certification process of the r22, but I am not sure of the original source of that information.