And of course, bitcoin sent to such burn addresses is not provably burned, and could be recovered in the future. The amount of provably burned bitcoin is quite low at 2,823 BTC.
What do you mean they can be recovered in the future? how?
In theory, it's possible that someone has the private key of those addresses or someone will be able to brute-force the private key of such addresses and can spend the bitcoin sent to them. In practice, it's very unlikely that someone will be able to spend them.