Fair points... This is definitely a novelty and "finesse" technique for sure and can have disastrous consequences if used in the wrong circumstances or executed poorly. When I first started using this technique I hooked a a nice 4lb largemouth bass on a deer hair popper that was wrapped around a few branches. Needless to say, that fish was not at the end of line by the time I sorted out the mess.
To avoid the "snapping the towel" effect, I typically lack a pronounced follow-thru but do keep forward motion with the rod. Seems to keep the fly from flipping upward at the very end of the cast. Also, I use this technique for short casts often just 10' in front of me and rarely >20' so the line speed is relatively slow which helps minimize errors.
Even if there is a little upward flip (<6" is ideal) I find its ok for the stillwater shorline obstacles I use this technique to penetrate. Most bushes/shrubs and other overhanging vegetation are more dense at the periphery of the plant; however, just beyond the tips of the branches many become less dense and create an almost cave like overhang. Put two of these obstacles side by side and you often will have a <1' wide, 6" high opening over the water at the edge, but then have a pocket of few square feet of water w/ a 1-2' ceiling. The narrower the opening the less effective the sidearm cast. If the undercut is wide I will use the side arm cast instead. Think of those places bass fisherman flip into using heavy lines and heavy lures to break thru the brush.
If the vertical clearance is 6" or less I will use the same cast and try and get the fly to touch the surface of the water just infront of the opening. The sudden deceleration kills the loop and shortens the cast a bit the fly will typically lead the leader into the brush avoiding any hang-ups of the leader on branches. Typically if the fly hits a leaf/branch it stops and drops to the edge of the brush w/out getting snagged.
Anyway, I agree not a high usage technique for most fly fishing situations. I probalby make this cast <50times per year and snag the brush no more than 10% of the time. I've had great success using it in very skinny waters with log jams, thick shorelines (alders, cranberries, even mangroves) and have dragged out some nice Pike, Pickeral, Bass, Snook, Redfish, etc... Although it can be used for any fly line weight or fly pattern I will concede that its horribly difficult to control small flies on light lines and much easier with stout leaders, big flies, and weed guards help reduce snags in case you miss your target or mis-time your cast.
I once knew a drug addict... He told me I have a fishing problem!