Anyone can decide what sats they consider to be exotic. You could decide you really want a sat mined during block 500,000. Or maybe you really want a sat that was stolen in an exchange hack. I think the "official" rarity tiers are ones that are convenient numbers (the same way that people who collect dollar bills for their serial numbers might want ones with a certain number of zeros).
By the way, there are a few blocks that I want sats from, so I set up a bounty: