Sorry Adam, as someone who has had 4 concussions in their lifetime, I can refer to MYSELF, in knowing that after the first one, two weeks is enough time to get back to 100%. Concussions become a problem only when they pile up on you. Troy Aikman and Tim Connolly for example, fully recovered from their first concussion, but were unable to respond to multiple ones down the road.
Playing hockey my whole life, my talent dropped only after my third concussion, and I have trouble reading and have constant migraines to this day. In between my first and second one, however, I was fine.
Like I said, you're wrong. You don't know what you're talking about and I hope you "knowledgeable athletic trainers" haven't been falsely preaching to you.