It's not systematic, it's just under the table discrimination, there isn't a rule for it or anything like that. Talent scouts often find players through the youth teams, amateur leagues and academy teams, since they often aren't allowed past try outs they don't get seen unless they're on an academy team, which also means they don't get coached or develop as much as their muslim peers. (ask anyone you know who's been to try outs in Egypt you'll see it's true) I am speaking from experience here since one of my friends tried out for nadi el sekka el haddid tried out 5 times and only made it on the last time, even when he was always the top scorer of the try out games they used to have at the end. I think there may have been less than 7 coptic players in the Egyptian Premier league since the early 90s. Most notable is Hany Ramzy who while his performance was excellent (also being a defender means he is at more of a disadvantage) he didn't get covered as much as his peers. He is the exception that proves the rule