Bigwig: You can’t just head off without your daily exercise!
This isn’t really an image within the game (Bigwig’s training spiel does not have a cutscene because it didn’t feel like a big dramatic event that I had to higlight. It’s just Bigwig being Bigwig.)
Realistically speaking, Pipkin COULD just walk around the rocks, but this is an rpg game, and you know that in their case, a portal between two rocks/tree stumps is the only reliable way to travel to the next map.
(Meta humor aside, even if he did walk around the rocks, what good would it do to have an enraged Bigwig after him? Is this really the fate he would wish to have? Would YOU want to have a pissed off Bigwig chase after you?)