> meaning of a trailing backslash is to escape the newline

That's what it does in this example. Don't have to use other cases, and don't believe I did.

In hindsight “escape” was a poor choice of word, but I did explain it and you omitted that from your quote: “meaning, in HTML terms, insert <br>”. And that’s not what reStructuredText does. Rather, at the end of a line, backslash acts like a line continuation character (… that only works in certain circumstances), a behaviour commonly found in programming languages inside at least string literals, but such languages aren’t using backslash as “escape the next character”, but rather they have a fixed set of escape sequences like \n or \uXXXX.