Bob:

The difference is in the hinging, and the gaps.

If you use Robart Hinge points, or similar, the surfaces can be hinged in a manner such that the surface LE has no effective drop on deflection, and then the thicker control surface gives only more drag, and not more effective control. To do this the hinge pivot line is behind the LE of the control surface.

Using "Skin" hinges, and a stiff skirt over the gap on the bottom, a la RC racing planes, again there's no advantage.

You mentioned the full scale planes. I don't know of any jets or fast prop planes that don't have the leading edges of the control surfaces in front of the hinge pivot line, this keeps the LE pretty much even with the TE of the wing.

You also have to remember that the gap on the full scale planes, with the inset hinges, is a very small fraction of one percent of the wing chord. On our RC planes, with conventional CA hinges, the groove in the surface is huge in comparison.

Or for an example of a full scale plane using the surface "Bump" trick, look at the vertical fin and rudder on a FW-190. Note the notches for the rudder hinges. When deflected to the right, the LE swings out, just a bit, to the left.

Bill.