Teams typically downplay injuries. I could see the Broncos downplaying the injury to avoid anyone questioning why they didn't bench him, as well as potentially avoiding injury report trouble from the NFL.
Schefter is typically pretty spot-on with his sources and according to him it was a torn rectus femoris. Which, idk, seems even worse to me.
Either way it's semantics. We can all see the huge drop off in his play from the Chargers game and on. Whatever it was, whether it was sprained or strained and bruised or torn, he was never the same.