Ideas are prioritized within a single business challenge (the theme an idea was submitted against), and that's deliberate.
Ranking a compliance fix against a growth experiment produces a number, but not a decision anyone can act on: they compete for different budgets, answer to different sponsors, and succeed by different measures.
Working one challenge at a time means every comparison is between genuine alternatives, and the output is something a sponsor can approve rather than a league table nobody owns.
Two ideas inside the same challenge are scored against the same weighted factors, so a comparison between them is something a sponsor can act on.