web browser – Why does Pale Moon (and probably Firefox) ignore the proxy when you forget to change the port from 0?

After reinstalling Windows 10 for the zillionth time, when setting up my Pale Moon proxy settings, I entered the proxy hostname but forgot to change the port to 443. The default was 0, which I only just now realized.

Looking at an “What is my IP address?” service, I verified that, with “0” as the port, and just the hostname filled in, Pale Moon entirely ignores the proxy and connects directly to the remote site.

As soon as I entered “443” instead of “0” in the port number field, that same webpage displayed the proxy’s IP address.

So basically, for a few weeks, I’ve been surfing constantly directly using my connection without realizing this, thinking that I was using the proxy specified by hostname.

While I don’t expect it to magically know that I meant to use port 443, I also didn’t expect it to just ignore this and “let it through”.

Should not Pale Moon be displaying something along the lines of:

Cannot connect through proxy.

Or something which would alert me to the fact that my proxy configuration was incorrect? Why would it just silently ignore it like this? That’s a major security flaw, even though I obviously accept some blame for being so careless. However, in my defense, I’ve had to do the same countless actions so many times now that it’s only human to eventually forget.