Okay, yes. I stand corrected. I was aware that there was some method that shifts some of the curation reward from later upvoters to early upvoters, but I did not recall the formula. I guess I thought it was more gradual than this.
The 25% is still there, but then it's factored and if there's a lot before it then it can diminish by quite a bit. Much better to be the only voter at 30 minutes (for a sure 25%), with some chance of later votes than to be a minnow voter piling on after the whales arrive.