You think Miller had his pass rush camp today? It was in June. A bunch of pass rushers attended.
I think it would be pretty easy to verify whether Young attended. There were also some virtual attendees (one writeup mentioned up to 500 if you included virtual participants).
I think it's also common sense that the Commanders, as is commonplace in the city they "call home", would lie or use some semantic technicalities to give the impression that they didn't have a rogue player go hurt himself on his own. Unless, of course, they plan to use that action as a reason to dock his pay or withold guaranteed money.
Edit: Looks like he wasn't actually there. Instead he was going through a grueling, 7 week long hair extension process that involved reclaimed pirate ship rigging.