I can't believe Dry Bowser took a very long while to finish the last track. It's as if he had a major confusion or a hard time doing so. Look closely at the map at 11:07.
I saw what happened. Dry Bowser, Yoshi and Birdo all respawned at the beginning but facing the wrong way, and their path correction failed. Yoshi and Birdo must’ve escaped eventually, but Dry Bowser is stuck in Limbo for eternity.