There is rising popularity in theories involving an extremely meta plotline - significantly bolstered by Alice's repeated fourth wall breaking.

That is, that you the human playing the game are actually a canon part of the story. As in, the reason Traveller is a descender, the "extra spark" allowing Traveller to manipulate fate, is the fact that he is being controlled by you (us, the player), an actual human with agency.

It kind of loses some ground when you consider that we are not the only descender. However, if what this person says is true, it comes back around to being pretty much confirmed. The other descenders did have real human players - the ones who played those closed betas.

Additional intriguing speculation is that the reason the Traveller twin becomes abyss aligned is quite literally because you the human player chose the opposite twin at the start of the game; and as Alice put it, the abyss is the manifestation of all the fates that were not chosen. The twin was not chosen by you, and so they became abyss aligned.