You realize light-timings are calibrated and coordinated based-on intended traffic speeds, right? Just because the speeders get stopped at the next light doesn't mean a too-slow driver doesn't get stopped by that same light after the speeder's got their green and gone-on.

Apparently you've never been on one of the roads I mentioned long-enough to notice they tend to have 4-lanes and lights spaced over a mile-apart, but even on a regular road with room to pass, demanding no-one do-so while you putter-along at just-over-half the speed limit is asinine. Drivers can pass farm-equipment that takes up a lane-and-a-half, stopped emergency-vehicles/cops, mail-trucks, busses, street sweepers and dumptrucks, but not you?

So where's the part about what your asking in any way resembles sharing the road again? The article doesn't even mention bikes, golf carts, or glorified mobility-scooters, btw.

Oh, and it literally says the opposite of what OP claims, even between motor vehicles moving with normal traffic, not obstructing it:

That means, on average, the lead of one car over the other remains the same after the light as before.

The results suggest the idea the slower car will inevitably catch up at the lights is something of an illusion.