It appears to be an app for a phone? I have no throttling problem on the phone in case that wasn't clear, but I don't care to look at the small screen and want to use my desktop.

I think they mean https://m.facebook.com - a lightweight web version.

There's also https://mbasic.facebook.com, which is even more lightweight and still allows you to send and receive messages.

I tried it. It's very ugly and featureless on desktop but it does load fast.

It actually used to have -more- features. I use it on my phone exclusively; once upon a time I could use messenger from within it. They removed that feature and now try to foist the Messenger app on me. So I don't use FB Messenger from my phone.