My favorite singles have a grist of about 5,600 ypp which is about 75 wpi. I know that spun worsted, such singles will have a twist of ~9 twists per inch, and woolen spun singles will have about 12 twists per inch. For more detail, see the formulas and tables in Alden Amos's Big Book of Handspinning, pg 383. AA formulas will get you to within 8% of the correct grist which is close enough for hand spinning and other online formulas will get you to within 2 or 3%.
Standard Ashford Traditional wheels have a ratio either 17. 5 (SD) or 14:1 (DD). That means with a standard SD traddy, one spins ~ 2 inches of 5,600 ypp worsted single per treadle stroke.
Thus, if one is claiming to spin 360 inches per minute of such single, with a standard traddy, then one is claiming to treadle at 180 strokes per minute, or 3 strokes per second. Working on Ashford stock DD wheel one would have to treadle faster. I want video of that!
Back in my bike racing days, we did sometimes pedal at 140 strokes per minute, but we were trained racers and we did not do it for very long. One does not treadle that fast while spinning fine singles.
Note that in fact, DD DRS has less drive belt slip, and is thereby much more productive than Single Drive.
DD DRS allow a different and faster drafting technique and is thereby much, much more productive than SD. IF you adjust whorl diameters, the DD DRS at a ratio of 14:1 will produce yarn much faster than the SD system with a ratio of 17.5:1.
Better flyers will increase the speed of an Ashford Traditional, and allow them to run at ~2,000 rpm or just under 400 yards per hour of 5,600 worsted single. (e.g., a sustained treadle cadence of ~120 strokes per minute with limited drive belt slip. At that cadence, a couple of hours is a very long day's spinning!) Anyone that claims more is not telling the truth.
With a better flyer and an accelerator, an Ashford Traditional will spin 5,600 ypp worsted single at a more than 560 yards per hour. That is the truth. With the accelerator, I can spin 560 yards of 5,600 worsted single with a treadle cadence of ~90 per minute. For an old cyclist, that is a reasonable cadence that can be sustained all day. Yes, it needs to be a double treadle wheel or the required force tweaks the wheel out of alignment in a few days. So both legs need to be going 90. If there is chafing, use lots of powder or get some of the anti-chafe goo that the runners and bikers use.
There are other wheels out there with ratios that should produce bobbin speeds high enough to spin 500 yards of 5,600 ypp single per hour, but the spinners that own such wheels report being disappointed with the productivity of those wheels. (Feynman tells us there is belt slip.) I have spun on samples of some of those wheels and they certainly did not come close to the productivity of DRS flier/bobbin assemblies driven by a accelerator.