Not sure, but if there were no red or green boat routes, and the blue route was only Contemporary (instead of Wilderness Lodge, Ft. Wilderness & Contemporary) they’d have more boats available to serve the gold route (GF and Poly).
Obviously Contemporary/BLT makes sense since you can walk. Not sure what the status is on the GF walkway (is there any chance at all that could open by the time resorts start phased openings? Guessing not, but it would be nice.) Once that’s open you could walk from Poly to GF to MK. Once that is done, all 3 monorail resorts are technically walkable to MK. A long walk, but a walk!

I could see that being a logical reason, except I doubt they’ll finish that walkway before resorts start opening.