It was a game of cat and mouse. Humans couldn't know what he was, and even if there were some that knew and accepted what he was, they were too fragile (and definitely too slow) to play a game like this with him. Bastion may not have volunteered to play this game, but he was entangled in it now, as Wolfram dashed after him through his territory.
When the smaller wolf stopped to try to see where to go, Wolfram struck, barreling into Bastion at almost full-speed and promptly tumbling over him to roll into the dirt rather ungracefully. He hopped back to his feet, once again dropping the front of his body to the ground to let out a sharp bark at his victim before letting his tongue flop out as he panted softly. It was not an act of aggression, but more of an invitation to play. You're too slow, little wolf.