DP2 as well as tons of other games were not meant to be 'speedrunned', that's why most people who want to run it setup rules and they speedrun it according to them. For example, did you know that there are tons of minecraft speedrunners? There is a rule: "As soon as you see trees, you have to hit menu and pause the game, then as soon as you unpause it, you start your timer and thats how you can get WR, if you get good time ofc.
In PB it would be even easier, as soon as you join team, you start timer.
Implementing ingame timer isn't crucial in order to get some competitiveness in jump maps, all you need is a few people eager enough to set these rules and to make it official and do some example runs.