I think they made him drop out because they knew a lotta players probably think he's a much better Dawnservant than WL. Wuk seems to really have done nothing for Tuliyollal before the expansion starts, while Koana actively studied abroad to bring back technology from overseas. Wuk Lamat only stepped out of the city to grab the strongest ally she could and bring them back to get her the best chances of winning (which also bugs me, bringing in allies is one thing, but surely "the person who just killed two gods, travelled to the edge of the universe and saved it" would be a bit far? They didn't know about the trials beforehand and if it was a combat trial, pretty much every other candidate could go "hold on... that's kinda bullshit").
Honestly, Koana has more full of a character than Wuk Lamat, and probably would have been a better MC. He's got more notable flaws, clearly being a bit quiet and introverted, having some self-doubt issues, but most interestingly, he pushes for Sharlayan technology very heavily (which could tie into some interesting conflict as he doesn't understand why people would do something in a worse way to preserve their culture).
The whole "both of them are Dawnservant" thing honestly just makes me think that Koana basically does the work, while Wuk Lamat is probably going to soak up the glory.