Sharing work is done in all areas of knowledge.Fair enough, but in my profession experts share each other's work all the time. Either to validate knowledge or to challenge it. But I am not a medical expert, so in medical cases I defer to those who are.
But if you actually understand a topic, you can speak on it yourself. I use other people's work all the time, but I use that work to BOLSTER and support my arguments, not make them.
You haven't positioned yourself as a 'master' of your topic, though. Your buddy has.