This is only one variable out of many. You can't make an educated decision based off of that little bit of information.
Do I believe harvesting the 6.5 year old negatively impacts the herd... No. There is no evidence that it would.
I don't think it would either, so let me share an observation here.
Many who claim to be practicing qdm aggressively advocate shooting only mature bucks because more mature bucks are said to be beneficial to the good health of the whole deer population.
They say that the presence of more mature bucks shortens the breeding season and reduces stress... then they shoot those mature bucks before and during the rut. [See Matt Brock's post above for example]
That seems to me to be a contradiction between the theory and the practice.
Killing only mature bucks immediately before and during the breeding season cannot possibly result in having more mature bucks in the population during the breeding season.
Sounds like your assertion that the buck population is usually skewed toward the younger age classes may actually be one result of qdm practices.