Hashrate drops if the hashrate drops.
The idea is to keep it from dropping by rewarding those who pick it back up
Personally, what are you asking abaout What if the block reward is based on the absolute value of delta in hashr8? I think this result is acceptable and makes sense in that it can contribute to the overall sustainability and security of the network, even if it potentially comes at the expense of affordability for each transaction. However, this idea has certain vulnerabilities that require further exploration of the application of block reward systems related to absolute deltas in hash rates.