There is a misunderstanding here. 2016-17 season, as a 20/21 year old, Fabbri was on pace for 46.6 points. For the record, this was after a slow start and he was really starting to heat up...who knows what he would have scored, but 50 was definitely possible.
The season you're referencing was 2015-16, Fabbri's rookie season. He started that year at 19 and turned 20 in January of 2016. That season he scored 37 in 72 (~42 point pace) after forcing his way into the top 9 as a 19 year old. He actually scored at a higher pace if you consider the fact that his ice time and opportunities were quite limited at the start of the year. Worth mentioning that he scored 15 points in 20 playoff games that year as a 20 year old.