They were not really burned bitcoin because they still exist and it's not the same with the others where we used the term burn where we literally deleted the token existence.
I'm not aware of this kind of address, how do they know that it is already a lost bitcoin or the owner is already dead? do they know the identity of the users?
They're sent to an address that is crafted specifically to make sure that the private key to the address would be extremely difficult/near impossible to find. They basically used whichever characters that they like at the start and made sure the checksum checks out at the end. Those coins are indeed burned because they are sent to an address for which it's corresponding private key could never be found, essentially removing it from circulation.