To start with, there is NO WAY that anyone can blame you for that if your tires are good. It will NOT cause skid unless it is extremely overinflated. A few PSI, like 2-3 I said, is within the error margins and the precision of the instruments used, plus there are quite significant differences between compressors also. In fact, under inflating causes more significant instability then the slightly higher pressure. If the tires are under inflated then the car will wobble in curves, and if you are unlucky you will lose control. If you skid with a slightly higher pressure then your tires are worn out or you are driving too fast, or something else is wrong. The cause is NOT 2-3 PSI extra. Also, if it is winter and there is any snow or ice then you WILL get better grip with slight over inflation, as opposed to under inflated tires. Also in rain a slight over inflation is better, it will give you better grip and LESS risk for skidding, not more. But again, tire conditions, as well as a lot of other things matter also, nevertheless, 2-3 PSI over is better then 2-3 PSI under. Another thing is that as you can see in that picture above your post, the RECOMMENDATION has a large variation. Also, the values are changing a lot between load situations, but do you honestly mean that if you drive with 5 persons then you pump 38 / 41 and then when you dump two of the passengers you immediately change pressure to 35 / 34 PSI ? because if you don't do that then you drive with over inflated tires according to your own warning with that car... after all, you said that
"You should never over inflate tyres" 