Isn't that a bit selective? They may be born a few months apart but they were born in the same year. Sancho may have left for Dortmund in 2017/18 but it wasn't exactly a breakthrough season in the first team - he had injuries and was playing in some youth level games, which is similar to how CHO was still playing youth level games that season and getting selected for the odd games in the first team. If you're gonna compare them, 2018/19 season for both would be fairer and...there really isn't any comparison there for obvious reasons.
And for argument's sake, you said Sancho had 1 goal in 12 games (he also had 4 assist by the way) but at least it's all in the Bundesliga - one of the major leagues in Europe. CHO's best work (if we want to call it that) in 2018/19 mainly came in the Europa League, which if we're being honest, all but 2 of the teams we faced were likely worse than 3/4 of the Bundesliga teams. CHO had 10 Premier League appearances and made only 1 assist, that was it. If CHO was really on the same trajectory as Sancho as you were talking about, Sarri wouldn't be so reserved about him last season.