Why is Google giving me a more complex route from hotel to Shinkansen?

Routing from Conrad Tokyo to take Shinkansen to Osaka, Google is telling me to ride the metro to Shingawa station and then get the Shinkansen from there... But it's only 2km to Tokyo station, my initial thought was to just walk to Tokyo station and get the train there.

What am I missing on why this route is being recommended? Is Google just trying to save me from getting lost in Tokyo station?

Thanks!