Actually, to be clear, my whole thing was prompted by @snakesss linking to this topic, which provides stats showing how the handicap system succeeded in keeping winrates around 50% back in 2020 – then just now I found this one about the 2021 ranking system, which keeps handicap winrates loosely at around 43% for Black* (though I guess that doesn’t necessarily mean the stats remained equivalent, and it might be worthwhile updating them if anyone knows how to and can be bothered).
So the point in discussion was that one would think the handicap system would be defective because of all these factors affecting online play, but surprisingly it didn’t appear to be all that bad (well, at least the 2020 system appeared to be good). And that’s where I came in with conjectures as to why that might be the case 
*by the way, I think the lowering to 43% winrate
might at least partially be caused by the rounding down that happens in the automatic handicap calculation. Since the number of stones is always calculated rounding down to a whole number, more often than not Black will have less stones than the actual rank difference. Down to 43% from 50% is still kind of a lot, though, so there are probably other reasons. In fact, looking more closely at those 2021 updated stats, I’m not sure I would say the handicap system works all that well anymore.