Here is a reply from the Mastodon thread that seems more plausible:
> @steeph @netspooky They're not hiding it, they're getting you to set up the printer over wifi, and only use the USB port after that. It seems if you use the USB port straight away it'll only print up to 20 pages then stop. They do this to get you to opt into hp+ and lock the printer in to use official toner. That's why the printer is so cheap