Despite what the ref told Bronco his reasoning was, the contact as pretty minor (Arellano did to a little bit of acting but was brushed into for sure) and I also did not think he was in a precarious position (he had pulled the kicking leg into his body, other foot was back on the ground and he was starting to regain his balance. In live action, I can see every reason why the judgement of an official would be to call running into.

For what it's worth, until the slow mo view, I thought it was for sure roughing on the live play watching on TV.