On https://www.speedrun.com/games Crossy Road does not show up unless you check "Show unofficial releases." On https://www.speedrun.com/crossyroad It also has "webgame, mobile" which are text and not clickable just like all other unofficial releases.
The game is official. https://www.crossyroad.com/ The creator, Hipster Whale, has the game on mobile devices (iOS, android, windows) as well as on the PC (windows appstore). It is also a "webgame" because Hipster Whale published it at poki.com.
I'm unsure why a mobile game or web game is considered unofficial. There are plenty of mobile games that are official games ( https://www.speedrun.com/games#platform=iOS&orderby=mostactive&unofficial=off ) and rightly so, because they are official. There are also plenty of web games that are official games ( https://www.speedrun.com/games#platform=Web&orderby=mostactive&unofficial=off ) and rightly so, because they are official.
So what constitutes Crossy Road as unofficial?
About plenty of web games being official - those are games which are set with the "web" platform, but not with the "Web game" tag which classifies the game as unofficial.
About why would web or mobile games be classified as unofficial, see Liv's response in the other thread.