I would imagine he was at the very least contacted about it. The ECHL might not be the most glamorous thing out there but it's ok money for a 20 year old. That said, he might not be looking at being a pro short term.
It's okay to go to school, but one would think he would ride the wave so to speak of being the top QMJHL scorer and get a sweet AHL deal that like you said, pays well for a 20 years old
Looking at capfriendly, Jake Lucchini is getting 85k minors salary, Brandon Baddock 110k, Khisamutdinov 70k, McNiven 75k, etc. I know they are contracted to the NHL parent club but I see no reason why an AHL deal couldn't be near 60-70k. That's way more money than any job you'd get at 20 years old and is likely more than he will make after getting a degree anyway.
It just feels like it would be worth it to try your luck for 2-3 years, save some money and go back to school if you fail. It's a very decent salary and with the upside that you may even make the NHL.
Plus, if you get established as a solid AHLer, you'll make more money than 99% of day jobs. I mean, Gustav Olofsson's minors salary is 250k. Think about that for a second. Some of these guys are getting rich from being #4 AHL dmen.