The only thing inconsistent with their primitive behaviour is the ability to cast spells, which could be attributed to the fact they are inherently magical.
I will have to disagree with you on that, I don't see animals with the tool use and complex social systems of the falmer. Aside from animated corpses, nothing else that uses weapons and armor have white souls. And even if they were "cavemen", that does not make then non-sentient, nor non-mer.
It really just sounds like your trying to justify a small mistake.