Remember years ago the Dolphins coach was Nick Saban and he had to decide which Quarterback to chose in the 2006 Free Agency. He was told by the Medical Doctors the injuries of Drew Brees and Dante Culpepper. I don't need to tell you if the Dolphins made the right decision do I? I hope the Dolphins Brass get experts on the condition of Tua before going all in.
The problem is doctor's are human. They tend to go with the more conservative guess. CYOA. People like to dis (correctly) Miami's medical staff, but they had reports from outside experts to help in the evaluation.
As for evaluating anything related to the human body, the variables are endless. Worse, the judgement of any evaluation can't be made until hindsight is available. What will be interesting is how every team evaluates Tua. I doubt one will pass and the others see return to perfect health.