I don't think that means what you think it means.
But regardless do not use frame interpolation on your TV at any setting. It's bad and looks bad and always looks bad.
600Hz doesn't look bad on plasma, though the 120Hz/240Hz soap opera effect on LCD/LED does look terrible.
Plasma a special case and is not interpolation. The 600Hz in a Plasma TV is the Sub-Field Drive rate not the screen refresh rate.
The Screen refresh rate on a 600Hz Plasma TV is still 60Hz.
If you want a more detail explanation this article does a decent job
Plasma because there no backlight it self emitting can appear smoother to a lot of people even through it still 60hz (not counting OLED). It also has by far the best blacks pre OLED. OLED through is even better then Plasma in this regard since they are also self emitting.