When I would train a player and invest money and time to get him in the National team and to have a very strong top player in my league and then the NT manager would share his skills with other players outside his own staff then I would be realy pissed off !
It used to be like that in Serbia too. Only few staff members knew NT player skills. We won 1 medal in more than 20 seasons, and it was Bronze.
Then we decided to make a change, and access to our database was given to anyone who wants to see it and is training potential NT players. In the next 20 seasons, we won 10 medals, 4 of which were Gold.
The interest in training NT players increased exponentially, and managers were able to understand much better how to train their players.
The overall quality of managers improved, which showed in club competitions as well.
It seems our communities think differently. No one in Serbia ever complained that the skills of their NT player can be viewed by other managers. It's quite the opposite. We managed to build a sense of belonging and trust among us. Even managers who never trained NT players, started training them. We worked towards the same goal, and everyone felt that they're part of the staff, and in a sense they were.
It also solved one other issue that we used to have. NT managers would often defend their poor results by simply saying that the team wasn't good enough. Since people didn't knew player skills, they couldn't judge for themselves if that is true, or if the results are underachieving.
Probably all other Div I managers know the skills of my Elakovic, even though I drafted him and he was never on a TL. Am I pissed off about it? Of course not. I'm proud of training such a beast, and I'm happy to get emails from managers asking me about his training.
Knowing an opponent player's skills can be helpful, but is in no way crucial, and much less important then what you're implying it to be.