i think this nonmenclature is carry over from overhand\underhand loops descriptions used to described for using as base to make other knot lacings off of. But, in loops it makes more sense to me. For when you go to cross a loop with WE\Bitters; the overhand loop forms more of a crossed turn\slide with the greater SP tension under the lessor WE. But, pull the same configuration the opposite direction; so that now what was once was the SP is WE; and WE is now SP; we have more of a hitch\pinch of the greater SP on top of the lessor WE.
As the initiating force realized before friction, SP will be the greater force. As the responding force after friction of lacing; WE will always be the lessor force. In the hitch direction of pull on crossed loop(underhand loop crossing self), the greater SP pinches the WE; the machine stands on its own bootstrap\resists or siezes against movement. Same crossed loop with reverse direction of pull (overhand loop crossing itself) the greater SP is more likely to slip under the lessor WE that lies on top of it. The hitch function giving more security as a module to itself; but the mechanics of the crossed turn \slip function passing power onto later parts of lacing strategy. Each has its own use that could help or hinder targeted functions.
The overhand\underhand knots though; are as you say. Because the line makes a 360 around self; so is just not over or under; but both. And further more the slip of a Crossed Turn always comes before the trap of the Hitch (pinch of greater SP on lessor WE) IMLHO. So, this reduces the trap force on Bitters\WE as we have the friction reduction of lacing previous to the trap of hitch portion.
This is similar to me to Clove\Cow. In that they are not just opposing loops or hitches to me; but rather a slip of Crossed Turn followed by the pinch of Hitch. Pulling either of these symetrical lacings from opposite end (so that SP\greater force and WE\lessor force switch ends) we have the same exact examination of slip of Crossed Turn primary; then the remaining force used as securing pinch of hitch. In same order, same exact flow, just like in Overhand Knot. In Clove; the fault of the SP\initiating force not immediately used at full strength to pinch down on WE\Bitters (lessor force end left over from SP after friction of lacing) to secure as maximum use of strongest force trapping least force is corrected in the Constrictor and some "Snug" hitches. Constrictor also especially holds SP and WE center mast trapping for balanced flow of force and also guarding SP\WE ends agianst warbling around\twisting out of lock.
So, i think you are right; and have used right hand\left hand to de-scribe differance in over\under hand knots; as it is more about orientation\presentation to eye or next part of lacing(like used to describe loops) than force flow mechanics (that i associate with knotting\rigging) to me.
edit: i guess the electronic ink of my pen here was so long winded that Gordon beat me to it!