That's incorrect. You seem to have some misconceptions about how decimation was used by the Romans. They did not use it on their enemies. Rather, it was used on their own military units as a disciplinary measure (usually in response to mutiny).

And the way it was administered was not to pick the strongest men. Instead, they used a lottery system like drawing lots to choose which 10% would be killed.

Since it was a form of military punishment, it would not have made sense to kill the strongest men. That would have reduced the deterrent effect, and also would have unnecessarily crippled that unit. Since the whole point of the practice was as a replacement for executing the entire mutinous unit, it would have been absurd to do so by destroying the cream of the crop.