Look - people used to complain about “cheaters” on the leader boards. I would prefer to avoid that term.
The point is that without some sort of cap or filter, a substantial number of the “leaders” are people who are using the site for a purpose such as “Look, I set up this program to run continuously and generate 100,000,000 points per month! Aren’t I clever!”
I think the cap should ideally be higher than 5000, but if someone earns, say, 120,000,000 points in a course with 100 words, so they have a million points per word, then their score is meaningless. There have always been users who figure out ways to do that - well, good for them I suppose, but whatever they are doing it has no place in a leaderboard.
I don’t understand why auto-grow would effect the cap. Can you explain what you’re thinking about the math?