This is an issue that I wonder about at times too! In my early biking days, the conventional wisdom was to remain seated and maintain a relatively high cadence by shifting to lower gears as needed. For me, steep hills are "fun suckers" and if possible, I tend to avoid them. Sometimes it's just not possible to do so 🙁. Occasionally, in those unavoidable situations, I've stayed in the current gear and went into "standing mode". At first, it DOES seem easier and I'm definitely going faster than if I remained seated and downshifted. I DO tire quickly tho and find myself wishing I'd stayed seated and downshifted. At that point it's usually too late to make the change (without going sideways on the roadway &#128580 so I continue to "honk" the rest of the way up the hill. While I hate to admit it, on rare occasions, I've had to dismount and walk 🙈 🙄.
I did the calculations RE: body mass (not BMI) and found mine to be 2.29 which puts me in the "sit and/or stand" group 👍. I find it a bit humorous that pounds and inches must be used to determine just how to best handle hills (if at all &#128540. BTW, a more precise method of converting centimeters to inches would be to divide centimeters by 2.54!