Earlier quoted context omitted.
This is a rare care where "astronomically low" is actually underselling how unlikely something is.
I mean, I found 10 used wallets not within 1000 pages of the first nor last page of his website in roughly 5 minutes. I’m fully aware behind the math of finding a wallet actually holding anything… but I was fairly weirded out to come across 10 wallets that quickly. Most had their last txn out roughly 2019.
I'd say odds are that the website is wrong, but you can always load those keys in a wallet and see if they give you control over the actual address.
If that works, I'd assume it's the case that some people have used weak keys (for example, a popular Ethereum wallet would actually generate 256 bits of entropy but accidentally truncate it to 32 bits in an operation), and any funds in those wallets will have been snagged long ago.
Point being: generate a private key properly, and no one will ever find it.
EDIT: I realize this is another page then the one I've seen previously, but I think the same idea applies. That one had support for Ethereum, too, and on the final page was an account with a balance.