I watched the novels algos carefullly for about 6 months, you're right, they are definitely different between app and desktop. From what I can tell, in the app, completed works are prioritized very significantly so they always sit a the top. That's why we always have the same few titles in the Trending front page on the app (at least for novels, as there aren't a lot of completed novels that continue getting a lot of interaction).
I think certain genres are also prioritized differently.
Also, for some reason in trending, you're likely to rank higher in the rankings when premium works are included vs when you're on the free to read tab. Can't explain that...