Even if we speculate - how a person not associated with them would be able to find the keys?
I think you misunderstood NotATether.
NotATether means that it may possible to get access to lost coins, if there are some information about the lost private keys or seed phrases.
Let's say you have a 12 word seed phrase. You know 7 words with their correct positions and you have lost 5 words. Now, you can't access your coins, but it may be possible that you brute-force the seed phrase one day.
Another example being if some desparate person had half of his seed phrase burned and posts a picture of the other half online in the hopes that someone can find it.