What could have happened to the mune on this Nanbokucho era tanto?

[Lewis B]

Does anyone else think the shaping of the mune looks odd? The togishi polishing stripes along the mune disappear towards the tip (at the red arrow) and it appears as if the ridge has been filed flat. Or is this an unusual stylistic design feature that I just haven't encountered before?

 

 

[Shugyosha]

Hi Lewis, 

Sometimes the mune got shaved on swords of all sizes so that kissaki could be saved. If you have “Facts and Fundamentals” there’s the suggestion in there that the straighter mono uchi in kamakura era blades results from that.
 

It’s hard to tell in this case as the hadori is heavy but maybe that’s what happened? 
 

Satsuma age is an extreme way to achieve the same result.