I produced a thread which detailed on a theory that the tsaesci are in-fact soul leeches whom gained the ability to use thu'um like abilities.
So this information about the akaviri kiai doesn't surprise me much. It even sort of adds to my theory, adding that Duskfang could be a kiai sword.
I don't think the lore we have could be explained with anything else other than having both. The Tsaeci were snakelike, couldn't wear armor and supposedly didn't use shields. The Dragonguard, on the other hand, were bipedal, carried shields, and wore heavy armor.
To add to this, there is two type of naming systems for the akaviri men and the tsaesci. The akaviri men seem to use one worded names.
The tsaesci on the other hand have two worded names, connected with a hyphen. Or at least that's what I gather from their descriptions.