I disagree Kradie and i'll explain why.
While I don't disagree the missions are officially made by Team17, speedrunning is not dictated solely/purely by vanilla content, also while the majority of games follow standard routes of the game, there are plenty games out there that have alternative methods/mods/categories/routes for speedrunning.
Not to mention, the updates DC and CS have done are official updates are they not? They don't get paid, they volunteered, community players who decided to take the game to the next level and has been accepted and is now included as part of the game officially, for example if you buy WA on Steam currently you get 3.7.2.2, which comes with ability to use big maps.
When you take these official updates as part of the game, all the content included becomes official as well, so making a map designed specifically for speedrunning can still be considered official if it complies with the limitations of the game.
What makes a speedrunning community and speedrunning categories official? A collective of players with the same purpose from what i've seen, so if we managed to get 100 people competing on the same gigantic map for many years to come, constantly smashing the world record and competing, supporting each other via Twitch and having followers/subscribers, it could most definitely become a thing, and could be considered "official".
GDQ does showcase the most popular/impressive stuff, I could be wrong but I think if there were enough people competing and supporting this, the level of skill is at least equal to many speedrun games shown on GDQ.