On July 23rd, 2020, both Half-Life Co-op and it's used maps received a major update, both with the gamemode adding a full game/global speedrun timer built-in (doesn't stop when the map switches) as well as some area changes on the map. Some other changes also include the speed at which doors open after the button to open them are pressed. These could affect timing of the speedrun. Would it be possible to maybe make change the current categories to pre-update and add post-update categories considering these changes? I'd like to submit a run for it possibly now that there's a built-in timer but the current rules don't really specify if these could be used instead of doing the between-map calculations and such. Oh, also, I can provide a download to a version of the gamemode before it got these updates in the case that anyone would still want to run it, again, only if these changes I recommended are implemented

I would have that change to the leaderboards like you said.

"adding a full game/global speedrun timer built-in (doesn't stop when the map switches)" This is useless if it doesn't stop on map switches, as in-game time is the only fair option as it's not hardware dependent.

Also generally, in speedrunning, people use which version is the fastest. If you see the old version being faster than the current one, you could upload it to Google Drive / something similar and add it to Resources.

Because of these reasons, there's no reason to split the leaderboard.