Why the demonstration fleet avoids the great-circle route

Why would the fleet not use the great-circle route?

Because merchant traffic made that route poor for operational security; a concealed fleet would choose a less observed track.

Naval route planning balances distance against concealment and contact risk. A great-circle track is geographically shorter, but it would bring the fleet near commercial traffic that could report its progress. The proposed demonstration would therefore follow a less obvious ocean route, just as Kido Butai avoided heavily observed shipping lanes on its approach to Hawaii. The fastest line on a chart was not necessarily the safest operational route.