EDIT: I tried it with my Super Luck Absol in Pokemon Sun.
Using Psycho Cut with Super Luck while holding the Scope Lens (Stage +3) gives 100% critical hit ratio (I knocked out 6 Mudbray consecutively with critical hits).
Without Scope Lens and only Super Luck and Psycho Cut, I only made 1 critical hit from 3 attacks. (My bad luck as it should be 50%)
However, this still coincides with Serebii's description. Serebii claims that the crit hit ratio doubles, which makes sense as 2x Stage +1 is Stage +2. Furthermore, as both Stage +3 and +4 give 100% crit hit ratio, we can never test this out. If Super Luck doubles Absol's Scope Lens-Psycho Cut from +2 to +4, it would still result the same as if it only increased it to +3 (both will give 100% crit hit ratio). It's pointless to continue this discussion.
The mechanics behind Critical Hits have not been changed in Gen VII.
They were, however, changed from Gen VI and still remain.
The critical hit boost was reduced from x2 to x1.5 and chance of critical hits at Stage +2 was doubled with critical hits becoming certain from Stage +3.
As for your question, no, the function of Super Luck has not changed. This ability only increases the Stage of the critical hit ratio. Serebii must have suffered a typo. A big one.
P.S. Who uses Serebii anyway? Pokemon Database has got to be the cleanest, organized and simple websites for Pokemon queries out there. Bulbapedia is also amazing when it comes to anime and completely wild facts and trivia on Pokemon.