I don't think that the dame blanche actually grows any quicker during the veg period, I think its just that it grows quite tall so you should flower earlier to keep it shorter. If you were to follow this route I would bet that the flowering period would be nowhere close to the advertised period.
The info for finishing times is whats supplier by the breeders and is often purposely under valued to make the strain more attractive.
You really want to give it a proper veg so that you have a mature plant otherwise you will lose out on potency. If height is an issue either consider using mother and cutting system or go with an indica and short flowering period.
That is all of course if you come from a legal state and have a med license, if you plan to take this advise and are in a state or country where it is illegal then you probably shouldn't break the law and I have not advised you to do as such.