After reading your post, I decided to take a better look at what the pedals are actually doing for me.
Purely observational, but this is what I noticed:
While the upstroke doesn't appear to create any real power, it does feel as though it assists in reducing force required on the downstroke
Not sure the mechanics, but it does appear to make a marked difference going uphill (my uphill stamina is garbage)

So if the upstroke isn't adding in any real work, is it really just allowing you to return to the downstroke faster than with platforms?
At least with my poor technique, on platforms, there is always a dead spot where my legs appear to being no work at all, as they wait for the cranks to return to the top of the downstroke (even if only for a fraction of a second)

Or, is the benefit that it reduces that positive work on the downstroke, and that's why I only really notice it in situations that require more work (acceleration, going uphill, maintaining speed in the highest gears)
If so, still seems like a more tangible benefit than many other things cyclists worry about (weight obsession)

Or possibly this: