I'm pretty sure that we decided the cosmetics should be tradeable as we didn't want to upset the majority of the community who probably will not be engaging in speedrunning. We know it's a niche activity and the idea of locking these rewards behind a game mode that might only be played by a small cohort of players could create resentment towards speedrunners. Note that the rewards on launch will be harder to obtain because there will be less reward points available, but I'll see how prevalent this feedback is and we can make changes if players prefer us to
Just an update on this: We can poll whether the cosmetics should be tradeable or untradeable, and we are happy to let the community decide on this if you would prefer.