It is true that this is wrong, grade is effected and has to be effected. You can pick XPs on the casual server and flight time and landings counts as well towards your grade. Otherwise you would never make it it to a higher grade that is needed for the other servers.
That said it really should have a mor clear description that says that you couldn’t downgraded on the casual server by doing it wrong but could get experience and grade relevant plus points.
When i first started flying online, I read the casual description, and it said that it didn’t affect stats or grade. I wondered how i was supposed to get to grade 2 if the casual server didn’t affect them. It took me a bit to understand the oblique reference to the lack of violations, as opposed to thinking that nothing on casual counted.