Seems like a cat in the sack. According to Transfermarkt, this year he only played in U17 tournaments and friendlies, doesn't play in the Egyptian Premier League at all. Can't be a huge talent, if he isn't playing even in the Egyptian league. Also born 01.01. is not always, but often a sign of fake birthday.
He might not be huge talent, because those are rare anyway. But not for those reasons you mentioned.
There is unwritten rule here that those who were born in the last 2 weeks of December or early days of January they will allaw you to register your newborn at 1st of January and as it is a "cool" date, while those born in October first few weeks can be registered as born on first of October (school deadline) so their kids can go to school a bit early.
It is possibly fake DOB but just about 2 weeks or something. It is about birthday rather than falsifying age. The later was once fairly possible back in the day, but not in his generation. And Egypt has no history of doing that for footballers. We barely have any success in youth levels. Our U17 history is laughable.
Obviously he didn't play in first team, it rarely happens for U23 players in a team like Ahly. He just became 18. They are the biggest team in Africa by wide margin and invest so little in developing youth. They wasted plenty of talents before due to that.
Even NT, in the game against South Africa, Marmoush was the youngest player in the starting lineup and he is 26, only one other player was younger than 29. Overall 7 were over 30. The youngst player that was called in the squad for the ACN is 24. This is fairly common, and big reason we were left behind in the past 15 years.
I've seriously seen some players being called prospects at the age of 25.
Salah had 46 minutes in the league at his age, he became a starter 6 months later in a team that finished dead last in the league. Fair to say he proved himself as a big talent.