Different reasons
It looks to me that nobody has really adressed your question. Here's my go:
I think the idea of full stick input is there in each case for different reasons:
In a significant xw T/O, there is more need of NGW assistance before 80kt IAS, for obvious reasons.
In the case of a pure tailwind component, there wouldn't be more need of assistance, only that whatever assistance is needed would be obtained, say, 10kt GS later, even more when comparing to a headwind component T/O. Higher GS, the AC veers off CL quicker for a given angle of misalignment. So, the elevator assistance is needed "sooner" (IAS-wise), hence the call for full downstick.
I have no idea how stick pos and elev deflection are mapped to each other over different speeds during the roll (it is said to be in direct proportion but that doesn't mean the proportion is constant for different speeds), but it makes sense to assume that AB just wrapped both wind conditions in one case and called for full down stick from the get go, just to keep it simple.
As for the second part of your question, I don't know. I wouldn't be surprised if, for certain thrust x TOW x CG conditions, the NGW became VERY light in the begining of the T/O.