The current rules (for the level leaderboard) say "Waves mode, use the speedrun option. Timer goes off ingame timer." Waves mode no longer exists, and neither does the speedrun option, which means there is no in-game timer to go off of anymore.

I'll be submitting a run for World 4 in Campaign mode, with time based on the video (where the starting condition is when you gain control in the first level, and the ending condition is when the boss shatters, exactly as in the old speedrun option). I recommend the rules get updated accordingly.