I think there could be several reasons for not wanting to address it at the time, especially the concussion. If he's not comfortable discussing it, or doesn't plan to ever mention it, that's ok. We wouldn't have even known about it if it weren't for Doug. As for Nebelhorn, withdrawing could have been due to the concussion itself, being very careful, or due to the fact that valuable practice time was lost because of the concussion and he needed more time to prepare. He could have even been sick. Medvedeva almost withdrew from Shanghai Trophy because she'd had a flu-like illness for a couple of weeks and hadn't been able to practice. There could have been a bug going around TCC. I'd be lying if I said I didn't want him to address it in some way, because I'm curious, but only when or if he's ready to. Have other skaters given reasons for withdrawing from Challenger events? I have no clue.
Men's short program at Skate America is TWO WEEKS from Today!!!

I'm feeling confident that he'll compete.