It says it right in the description for the Midwest finesse rig plastic mold on the do- it website.
I think where the confusion is coming from is Chubs is that you are taking "floating" to literally. The Essential series plastic if well mixed and no salt or other weighting media added to it is slightly better than neutrally buoyant. Lamar's picture clearly shows a bait ON the water. Now add the jig that the bait was designed to be used with, even the smallest, and that buoyancy is gone except at the weighted end which will settle in such a fashion that the remaining bait will stand up readily because it is still buoyant without any weight to hinder it. Other jigheads may not allow this to happen because they're not designed to work specifically with this plastic bait like the Midwest Finesse Heads are.
Consider too that glitter and hi lite/pearl additives weigh something and if lots are added to the plastic they can affect the ability to float and some colorants alone are pigment heavy, white and chartreuse come to mind quickly, and if those are added heavy enough to opaque the baits color they too can negate the ability to float.
Floating is a term that rides a fine line and we, as plastic makers, can do a lot to change whether or not the plastic can float or not.