I bet its the idea of ESPN directors to put it out there.
I mean, if you put it logically, he should have pumped up his fist in real time, as soon as James Young was called.
But the feed went for a few seconds before they showed Bill fist pumping (which is awesome BTW). No one gets excited and waits for about 5-10 seconds to fist pump. Now I know it's live, but there should be some TV magic there where in the director probably said (let's put Simmons' fist pump on the show, will be good TV). And then him realizing (or being told) his camera is on made it even more priceless.
But that's just me.