That seems absurdly high if you're talking about fully remote.

We're talking about advertising for jobs on Hacker News. Maybe there is just not much value to advertising location-specific jobs in these threads.

You're almost certainly right. But it also means that the postings are very unrepresentative of the broader market.

There's probably a bias given that this is a website with global reach. For any company posting, almost all readers are not living nearby.