The first diagram is to do with some tail rotor issues. On a helicopter with counter clockwise rotation, viewed from above (basically speaking, not French or Russian), the tail rotor thrusts to the right by forcing air to the left. Thus, wind from the right is the same as putting the tail rotor into a climb condition. Whilst wind from the left is akin to a descent. With the wind from 'back and left', the tail rotor is effectively in an oblique descent. The wind is pushing against the rotor flow and with the oblique angle, leads to a few other aerodynamic nasties. Both cases lead to differing rotor effectiveness and power requirements.
The second link is looking just at the stability of the tail surface (and the flat plate effect of the tail rotor) which is stable with wind from the front i.e. keeps the nose into wind. Whilst wind from the back has the same effect of trying to swing the nose into wind which may not be where you want it to be!
Thing with these kind of sites and some text books is that its all given separately, whereas in reality all of the effects are occuring at the same time. Which one is 'dominant' will depend on a large number of factors.
Helicopters, you've got to love 'em!