Using this lens alone produces dramatic falloff in both the the highlights and the shadows, both indoors and outdoors and the histogram used is only a middle third.
I haven't noticed any difference between either of my 14-140mm lenses and my other lenses. But you got me curious, so I just put together a quick and dirty comparison
between one of my 14-140s and my 75mm (which is generally considered to be one of the best m4/3 lenses currently available). I deliberately chose a very non-contrasty scene similar to the one in the pics you linked to, and yes, this does result in the histogram being bunched in the middle. But note that this is for both
lenses. There is very little difference between the histogram for the 14-140mm and the 75mm. (And what little difference there is is most likely due to the slightly different framing -- I did say this was "quick and dirty".)
Are you sure you used the same settings when you tested? If so, you may have a bad copy.