I'm very familiar with the soap opera look from these sort of interpolation features. Either what I'm reading is incorrect or your information is outdated. MotionFlow has several different types of settings with varying effects, at least on the 2013-2014 Sony TVs. It would appear MotionFlow now has an option that is similar to the strobing light used for 2D Lightboost, or maybe it inserts black frames. Either way, not interpolation, and only increases the input lag by about 5ms (still putting some of these Sony TVs below 30ms input lag, still some of the best on the market). I've even heard some of the interpolation methods on the Sony TVs were designed to not produce the soap opera effect somehow, though some of the options are what you'd typically expect from interpolation.
If you scroll down on this TV example, you'll see info on this in the MotionFlow Impulse section:
http://www.rtings.com/reviews/tv/lcd-led/sony/w800b
I have heard it works well for 60fps but not 30fps.