Like, can I just start 20k threads in WebAssembly and reboot anyone who visits my site?
Obviously I'd expect the browser to guard against that... but I expected the OS to as well, so my expectations may be way off!
But probably not on Windows 9x, maybe not even on NT4 (although, NT4 was pretty solid), and I wouldn't expect good results on Linux or a BSD from 2000 either.
But macos has lowered my expectations. It's a mash of FreeBSD from the turn of the century, with Mach from earlier, and whatever stuff they've fiddled with since then, plus a nice UI layer. They don't regularly pull in updates from FreeBSD, and the killed their server line (which was mediocre at best anyway), so when it panics if you do something weird, it's not unexpected.