That's too bad, FT.   I can see how this could happen if a skinner's PC has the Environment setting set to off.  They would never know anything is off - the skin would alway look Ok to them.   I stopped skinning before these bump and spec map files came into use, so I don't understand how to use them or check for problems.   Seems to me this kind of thing would only reveal itself on a different PC than the skinner has.  Perhaps skins need to be looked at on several different configurations?
I have seen this effect on some P-51 skins too.  It makes them look like Nevada air racers, not warplanes.