I will admit I did not read every single post in this thread. But I read quite a few. What people seem to be missing regarding Satoshi's quote in this case is the context behind it.
The context of Satoshi's statement has been pointed out before, IIRC.
Each of the 20 or 50 addresses in each of those wallets had a different private key/seed phrase associated with each one of them.
This reads weird, especially the highlighted "seed phrase" part. In a
HD wallet all derivable keys are also unique, same as random keys of a key pool of very early wallets.
Each of the 20 or 50 addresses in each of those wallets had a different private key/seed phrase associated with each one of them. There was no single backup phrase that you could write down.
Early wallets of Bitcoin standard client software (Bitcoin-Qt or Bitcoin-GUI, don't remember the exact name of it) initially created a pool of 100 independent and random keys. Making backups regularly of your wallet file was the only way to preserve those keys and was highly recommended, because you couldn't rely only on old backups. When the key pool got exhausted the wallet generated another new batch of 100 unrelated random keys which then weren't in your old backups prior to the key pool extension.
If you lost your current wallet file or replaced it with an old backup that didn't have the new batch of fresh keys, you could loose access to some or all of your coins if those were controlled by newly created keys. That was a significant problem of a wallet without deterministic keys (BIP-32 derivation).
See e.g.
https://en.wikipedia.org/wiki/Cryptocurrency_wallet#Non-deterministic_wallet