Nope, I'm wrong, there do seem to be yataghan with the weird "integral bolster" :
http://www.vikingsword.com/vb/showthread.php?t=3466 but then it is really small and it looks like that of a khodme
So here I'll ask Ham and Jim and others with experience on Ottoman weapons to say whether the octogonal "bolster" is found often enough on blades produced in Turkey/Asia-Minor/Caucasus.