I must still respectfully diasgree with you about a soft-action, full-flex (one that bends to the cork on nearly any cast) casting further with a DT than with a WF. Likewise, I must respectfully disagree with you about a soft, full-flex rod becoming overloaded with a WF line, while not becoming overloaded with a DT.
The first 30' of standard WF and DT single-hand lines are basically the same taper; but more importantly, they weigh exactly the same, within the small variation allowed by the AFTMA single-hand line standards for a given line weight number. However, after this initial 30', things change very rapidly regarding how much weight the rod is asked to cast.
The DT line continues to have it thick belly (the thickest and heaviest part of the line) go on for another 40-60' until it reaches the 5'-10' long back taper at the end of the line. On the other hand, the standard WF line has a very short back taper at 30' (2'-3') followed by the thin running line portion of the line, which weighs nearly nothing in comparison to the thick belly. Thus, a DT line weighs a lot more at 40' than a standard WF, and at 50' the DT weighs about 2x what the standard WF line does.
Therefore, the much heavier DT line at distances greater than 35' would overload a rod very easily; however, the lighter WF line at the same distance cast as the DT line would not overload the rod assuming you are using the same weight DT and WF line.
I also must diagree with you about tournament rods not flexing. Granted a rod used by a tournament caster in a tournament is much stiffer than those used in fishing. However, this doesn't mean the rod doesn't flex. In the hands of a very good distance caster, tournament rods do in fact, flex and bend. Let us not make the mistake of thinking that just because most fly casters do not have the technique and power in their casts not to bend a tournament rod very much that tournament casters cannot get that same rod to bend. They can and they do get those very stiff tournament rods to bend.