Why do backslashes prevent alias expansion?

Question

In the first part of my question I will provide some background info as a service to the community. The second part contains the actual question.

Part I

Answer 1

Historically, and maintained by POSIX, quoting any part of the word causes the entire word to be considered quoted for the purposes of functions and alias expansion. It also applies to quoting the end token for a here document:

cat << \EOF
this $text is fully quoted
EOF