Not sure you have to be running flat our for it to be a bump.He didn’t choose to bump though. If he had chosen to bump he would have put Day into next week. He stopped and braced for Day to run into him, which he duly did.
Choosing to bump and bracing for contact are two completely different things.
Call it what you will though, but he had other options
When you have a guy coming at you at full pace and perform that act you are a chance to cause damage to the head because there is still going to be two players hitting each other at pace
Get low and brace to tackle or reach for the smother.