He has displayed it before. For example, we were blowing the Browns out in 2016. It was 3rd and long in the 4th quarter and Dak threw incomplete to Witten instead of deep to Dez. Dez got frustrated, walked into the end zone, raising his arms in the air and looking into the sky shaking his head in disgust. This is the same game he loafed on the 3rd down scramble instead of blocking for Dak which got him chewed out and the same game he argued with officials for pass interference calls instead of battling for receptions.
When you're frustrated you didn't get the ball in garbage time of a blowout game you're winning, it has nothing to do with passion and winning. It has everything to do with being selfish.
Something occurred after that game though because his attitude changed. He became a team player the rest of that year and it really didn't resurface until the Seattle game in 2017.