You say that, but that actually has happened
City stopped cooperating with UEFA because someone at UEFA was leaking information to certain journalists, who kept reporting exactly what documents City were passing to UEFA These journalists had a close long established relationship with Rick Parry, former chief executive of Liverpool, so it was quite obvious where the press leaks were coming from
City then drew the line and refused to cooperate no further
After CAS, City made a formal complaint about the press leaks, UEFA then said their ethics committee would open an investigation
Parry left his post at UEFA to become head of the Football League and the investigation evaporated, never to be heard of again