There are a TON of little things that are very poorly documented in game, outside of the tactics, where the in-game info is well known to be outright lies.
Examples--there are active threads right now that ask for explanations of home grown rules because the in-game explanations suck. (And they're bugged anyway.)
U20 rules are poorly explained. Competition requirements for the Italian U20 say only one over-20 player can be played, but that's not true. It's really players born after some date 20 years ago that is either not in game or hard to find. Which of my 20-yo players meet the cutoff, and which don't? I don't know!
The foreign player rules in China do not behave even vaguely like the in-game explanations. I don't know whether the written description or the implementation is incorrect, but they are strikingly different.
If you have a rule, as you do in Italy, where foreign players can be signed only if they have certain qualifying national team caps, why don't your scouts supply the information? It takes a lot of research on several different screens to figure it out by yourself, and that makes it easy to make mistakes in the calculation