The only thing here I might argue about is the idea that 10 mg/L is optimum. What's the optimality criterion? IMO the 'best' amount of oxygen is strain and pitch rate dependent. The latter is easy to see as, presumably, each cell will consume a certain amount and, thus, the more cells in a liter of wort the more O2 you need to supply to that liter. The other (strain dependence) is just common sense.
As for the accuracy of the calculation - that will depend on the accuracy of the flow meter. The typical gauge type flow meter measures pressure drop across an orifice and is accurate only against a given outflow pressure (typical medical regulator). If your oxygenation stone is under a foot or 2 or wort obviously the head adds back pressure.The pith ball type meters depend on the density of the fluid and thus, for accurate readings, you must have one calibrated for oxygen. The other factor is insuring that no bubbles are indeed breaking the surface. There are bubbles that are too small to see (hence the flashlight trick for early detection of the start of fermentation). Putting all this together I'd say the attainable accuracy is 'close enough for government work'.