Now you're rationalizing.
Fact is there is NO historical evidence of a reverse bladed sword in all of the very well documented history of Japan. Nor is there an example in any sword museum anywhere. It is also true that the author of the manga is on record as having said that he did in fact make it up. This topic comes up all the time, and it is routinely shot down. Feel free to surf over to http://www.e-budo.com
and search the Sword Arts forum. Also search the forums at http://www.swordforum.com
Those two forums are where most of the academic types hang out. This topic has been done to death.
They simply did not exist.