How can wingtip vortices affect the direction of the relative wind in front of the leading edge?
Please don't believe everything you read. You healthy scepticism is your best defense against the nonsense you might read about wingtip vortices.

What causes the flow to increase its angle when approaching the leading edge is the low pressure region above the wing. This is not only the main contributor to the wing's lift, but also the reason for the flow pattern ahead of the wing, in combination with the overpressure region around the stagnation point.

Please read this answer and let me know if something is left unclear.