First off, just call it effective field goal percentage or if you want to dig even deeper try true shooting percentage. There is an actual statistic for scoring efficiency.
That being said, you think that is the reason he isn't going to the NBA? LOL.
The likely 3rd pick in the NBA draft this year was worse than Yoeli. His name is RJ Barrett and his eFG% was 50.6% and his TS% was 53.2%. Meanwhile Childs was at 53.8% and 56.9%. So why will RJ Barrett be the 3rd overall pick and Yoeli not at all if this is the reason that Yoeli isn't making it to the NBA? The simple answer is it isn't.
The NBA is about projecting skill and how it will stand out in that league. Stats are considered, but they are a small piece of what the NBA is looking for.