You snipe at 5 minutes. Now someone else snipes at 4:57. They only give up 1% of rewards but gain far more than that by being ahead of you. You now decide it is worth it to snipe at 4:54. Repeat. As a result, much of the curation rewards on useless curation is then returned to the pool to be used elsewhere.
This already happens BTW. Many votes on known-payout posts are made around 5-8 minutes I believe (I haven't checked the exact numbers recently) even though the penalty timer currently runs to 15m, returning curation to the pool. That part won't change much with HF21, although the higher absolute curation rewards may drive a bit more activity.
I understand that situation, yes - though I don't have any real world data on it. I was just thinking that a significant increase in the amount of curation rewards available would lead to a variety of attempts to focus on gaming this aspect of the system. Hopefully people find it pointless and do real curation instead - we shall see!
People will go where the money is sure. Some will focus on gaming this aspect but that offers a benefit to everyone else when the rewards are returned to the pool. Early votes on known-payout content reduces the effective curation rewards there from the nominal 50% and makes looking for lesser-known high-potential content (where you can still get the full 50% or close) more attractive to others. Specialization is inevitable.