Right. But what I’m arguing is that there’s no way to know if they can be spent or not, so we shouldn’t assume any Bitcoin are “unspendable”.

I could give you an address and tell you I lost my private key and have you mark my coins unspendable, but I could still have my key and move them 20 years later. Even in cases where it seems very legitimate that Bitcoin have been lost, since there is no way to verify for certain that they are, they effectively aren’t. And they shouldn’t be treated as much when we are calculating total supply.