I would think about this a little differently. The average points per NBA game this season rose to 114.2 points per game, up from the mid-90s in the late 1990s and early 2000s. Granted, it used to be even higher -- around 120 per game back in 1960 when guys like Wilt Chamberlain were putting up those numbers.
So if you were to compare it, say, to that 2000 season when it was more like mid-90s for an average game -- Shaq and Iverson had 9 and 8, respectively, 40+ point games. Then Grant Hill had 4, Gary Payton had 3, and then it's a couple players (Hughes, Carter, Duncan) with 2 and a handful of 1's. So just the top five players had 26 40+ point games.
This year as you noted the top five players had 17 total 50+ games. In 2000, 40 was just over 40% of total points scored in the game (something like 42%). Now, 50 is just over 40% of the total (43%).
So from the perspective of equity within the team, the top players are overall not scoring more as a percentage of total points, they're just scoring more nominally because there are more points to be scored. 50 is just the new 40 because 115 is the new 95.
I haven't looked at this in-depth beyond the initial hypothesis, but I would think it'd generally hold.
EDIT: Just connecting to your comment that it's the most since 1960. Since that's the peak of total points per game, that probably helps support the overall point.