They probably recommend a charge because they are NiMh batteries - meaning they lose some of their charge as shelf life increases. If they have been sitting around unused for a couple months they could be at 50% or less of their original capacity. The recommendation for a charge before initial use would seem to be certain that they will achieve their rated capacity for endurance and not strand a rider in the dark after 20 minutes.
Eneloop technology (hybrid batteries), although posessing a lesser total capacity (2000 vs 2700mAh), hold their charge much better than standard NiMh batteries. Hence the term precharged when purchasing them. You could put Eneloops directly into your device without an initial charge.
By the way, I am not familiar with what type of batteries Dinotte uses and am merely commenting on what I believe the issue is.