That's the one - nil wind (or 7kt for older UK aircraft).
However, you are missing the point of the comment.
For example, if your aircraft had a max crosswind limit of, say, 40kt, and you had something approaching that on the day, you could find your actual Vmcg (as opposed to the book figure) increasing by something in the range of 20-50kt depending on the aircraft Type. Have a failure in that grey area with a low scheduled V1 .. and you might find control to be extremely interesting but, possibly, only for a short time until you found yourself in the grass.
You could well be taking off with a V1 somewhat above book Vmcg .. and still get bitten big time if you believe you are ironclad in a strong wind by virtue of the certification Vmcg animal.
The point is to be aware of the potential problem and, where feasible, avoid min speed schedules ..
I don't know the actual delta for the 738 but, if I may hazard a guess, I would guess something in the 1kt/kt region.
I may have an opportunity to ask the question of a knowledgeable chap next week .. if so, I will come back with something a little more accurate.