I don't independently remember the break down at all - that's why I was hedging a bit with my comment re their respective situations. But Eichel also got off to a slow start. I think it will benefit Matthews to be starting the season coming off the WC.
Even if Eichel's rookie situation ends up being more advantageous than Matthews', it's still hard for me to envision Matthews having much trouble hitting 50 pts...I mean, Bozak and/or Kadri should be able to handle the harder match ups than Matthews ought to be expected to...and I assume Matthews will be PP time... He also doesn't have the type of glaring deficiencies (skating, strength, or defense) that typically cause very young players to struggle.
Stamkos started off with a really bad coaching situation - and picked up fast after the coaching change. Stamkos was also playing as U19 player (I don't think he was, as a rookie, ahead of where Matthews is now). Tavares was hampered at the time by his skating...as with Stamkos, I suspect Matthews is ahead of where Tavares was at the time b/c of skating alone...but honestly my first hand memories of their rookie seasons is vague at best.
Of course, it's true that there might be situational issues that cause Matthews to have lower point totals...but I still think that 50 pts shouldn't be that much of a problem. If he doesn't get there, then I suspect it will be situational/usage (I'm not proclaiming 50 pts should be "easy" as some sort of "set up" so I can criticize him later or anything).