Just a guess, but maybe a typical bot has a webserver, ssh server, some other servers running on the same machine, whereas a typical Visa applicant doesn't.

Or a browser automation server (Marionette/CDP). I seem to remember watching a presentation where it was mentioned you could detect them this way, <s>but I don't remember where or what it was called.</s> this one: https://www.youtube.com/watch?v=4nZD6ee2Xo8 (WHY2025: Stealth Web Scraping Techniques for OSINT)