zzuf, I hope you are not actually a pilot ..
Now, I have known zzuf for, probably, near on 40 years. Might I suggest that the good LS discontinue the line of argument lest you, surely, lose, as lose you will if the discussion revolves around certification. As to whether zzuf can fly, as I recall, I have only ever flown with him once .. and I got out of the aircraft, shall we say, green with envy .. now, why couldn't I fly half that well and that on one of my best days ? For interest, he had never flown the particular aircraft Type previously, it was a mongrel of a day .. and he flew it like it was on rails out on a nice nil wind morning at dawn with a big high sitting over the place ... I think he qualifies as a more than passable stick and rudder chap.
Of course crosswind does not have any effect on Vmcg.
Zzuf is, naturally, absolutely correct. However, he is talking about the certification animal and it, quite correctly, has no interest in the wind on the day.
Anybody who doesn't understand why a crosswind component effects Vmcg is not, I hope, flying real aeroplanes.
Leaddie, on the other hand, is talking about handling problems on the day when the wind might be whatever .. and Vmcg, as she is wrote in the book, might not be all that relevant to the pilot's immediate problems if the speed schedule is on the minimum .... in such conditions, with an unfavourable and strong crosswind, the pilot might well find himself below the speed at which he can control the aircraft directionally. One circumstance in which the aircraft operation might well be perfectly "legal" but the bird heads off into the weeds regardless of what the pilot might be doing .. unless the pilot be sufficiently astute to recognise that the takeoff needs to be rejected albeit above V1.
For interest, the following rules of thumb are probably not far from the mark -
(a) for a twin, be prepared for the defacto-real-world-"Vmcg"-on-the-day to increase by around half a knot per knot of crosswind, or more. This is based on OEM data for one particular twin jet (with which zzuf was familiar many years ago, as a yellow-coloured example). Note that this has no effect on the certification Vmcg, only the pilot's real world handling problems.
(b) for a quad, probably in the one knot/knot plus region...