Hi Mark:
While I agree with you in general, it is important to consider the relative age of most new recruits. When I was seventeen, I wore a size 7-1/8 cap. At age forty-one, I wear size 7-1/2. Stature has certainly evolved over the generations. Were Germans appreciably smaller than other Europeans in 1914? I doubt it. We should also remember the Pickelhaube was worn above the occipital bone, where the circumference of the skull would be smaller. I believe the purpose behind this was twofold: to enhance the perceived height of the soldier and to prevent all those threaded bolts and fasteners from contacting the head.
By comparison, the average Stahlhelm appears gigantic. When the function is protection, an entirely different fit would be required.
Human morphological characteristics notwithstanding, let us return, for a moment, to the eBay listing.
Here is an exploded view of a feature unique to this helmet. Note the deft manner in which the peak, peak trim, and liner are assembled.
I don't know about the rest of you, but I see nothing to distinguish this item from the ubiquitous trash characteristic of this seller. To my thinking, the only Kinder connection is that this helmet may have been assembled by child labor in some forgotten corner of the far East.
Perhaps it would be "kinder" if daylight had not been shed upon it.
Chas.