The checksum is only for the users wallet. If Proof of Burn (PoB) works as promised (unrecoverable coins), you must create an invalid address and provide a custom wallet to send to it.
If the Burn address were to be spendable, then that private key's discovery will be prioritized.
With so many potential PoB solutions hitting the market, it makes sense for each team to disclose why they chose the burn address they did, so that they can become standardized.
Proof of Burn is just nonsense.
