To be clear, the "player" picking a number is the fictional optimal pilot, not the deck's submitter. The picking a number is just how shortcutting loops works in Magic, as in the tournament rules WoP posted above. Loops can only ever go infinite when they're completely inescapable (like 3 Oblivion Rings with no other targets), otherwise you have to choose a number. Your reasoning about optimal plays overriding loops isn't perfect, because a player with Nomads en-Kor who's going to lose could optimally just activate his 0 cost ability forever. Thus the distinction is necessary (assuming we agree that's not a good outcome.)
This not being clear did affect the scoring for WoP taking infinite turns, and raises questions for two decks this week. I imagine it has probably been relevant before with Rishadan Port or a tapping creature being relied upon infinitely for a draw, or someone paying indefinitely for Tabernacle to keep a blocker up. I think there's agreement that players shouldn't be forced to end loops in those situations, but that's not the conclusion we came to with WoP's deck last time.
I'd ask that something on this be added to the rules on the first post, as this is a difference to the regular Magic rules.

