Not necessarily, we could reach a point where theoretically it is possible to crack elliptic curve but still prohibitively expensive except for nation states. At that point or near that point, miners would likely agree to engage the throttle.

Presumably the vast majority who had their key would move the coins before the throttling takes effect so in the event of a 'slow takeoff' quantum scenario where quantum computing is expensive or nation states don't want to divulge the capability there could be no demand for the 1btc slot. If a lucky individual forgot about their coins (likely an early 50btc block), it only takes them ~8hrs to transfer at the normal txn fee.

Only those with access to legacy coins can compete for that slot.

The main advantage is it delays the transfer to the mining reward to the last possible moment, IE the trigger for the transfer to the mining reward likely only happens if there is sufficient contention for that 1btc slot because legacy wallets are getting cracked.