It returns a resource but I wouldn't say it's working.
I found it confusing - if a URL is "offline", I'd expect some kind of error message like connection refused or no such domain. The URL here is not "offline", it's the BL that's offline, and the BL isn't a URL.
If it displayed the Cloudflare 502 Bad Gateway error page, would you consider the URL to be offline?
There's no Cloudflare here, but I see it as conceptually the same thing.