I'm not a chess master or anything, so I'd be curious to hear what an expert player thinks of this.
I also wonder if adding a kind of heat graph layer for indicating "player had this position in reach" for the proportion of the game, might provide additional useful information about the balance of territory control, or whether superimposing the pieces at the final position might make it easier to scan.
EDIT: ok, after staring at the clock faces on each position some more, I can get an intuition by looking at whether it's colored in all the way through as to whether a piece was likely captured there or moved to a connected position (seeing if it resumed existing at another position by whether the angle of coloring lines up) but it's still incredibly difficult to determine which piece was there at the endgame. Mid-game is completely muddled for me even with understanding the clock-shading better. The most I've been able to get from a quick scan is whether there was a lot of capturing or if the game was more about positioning.
Perhaps the element that makes this kind of visualization difficult to apply here is that both extremely long games and very short games are having to fit in the same amount of visual space. The two primary dimensions are number of circles and number of independent segments in the circles, and even for short games that reaches some level of too numerous to count in a scan.