You have to understand that in a lot of yaoi mangas not a lot of seme's get flustered. They are a rare commodity in this genre.
I've read over a thousand BL manga, and I know they are not as rare as you seem to think. Not sure what that has got to do with my comment, though. My opinion still stands.
I agree with you. Feels so robotic and turn off.
There's a lot of manga wherein seme get flustered, but when it comes to Butler type seme, they almost always doesn't show emotion.
Ei is way too cool and perfect for my taste. It's so boring with a seme who is never flustered.