I have retimed another game's leaderboards with milliseconds(https://www.speedrun.com/boomerang_fu/news/yxyzkz6n).

I just came here and start doing some runs, but now I'm thinking why it also doesn't enable "Measure run times in milliseconds"? I think it's not a good choice to disable it and only have time with second precision for a run time.

they're just not used, no real answer really. If there's ever a tie to the second, it could be used to break the tie.