I've seen it and at least in Chrome it seems to be treating all URLs which are based on an IP address as "local", regardless of the class of the address.

I'd be inherently suspicious of any website in the wild attempting to contact a bare IP address. Aside from localhost, my default assumption would be that such a website is either trying to circumvent my hosts file (or circumvent my other DNS configuration, e.g. pi-hole or DNS-over-HTTPS), malware trying to reach a command-and-control server, or malware trying to circumvent my adblocker.