If you intend to type or paste quotes, you still need some additional escaping. And on the other hand, most substrings of (non-quoted) escaped text are themselves properly escaped.

ksh's %q prefers quotes; for your example it prints 'text with spaces', and for the article's example,

    $'This string \'has single\' "and double" quotes and a $'

vs bash's %q,

    This\ string\ \'has\ single\'\ \"and\ double\"\ quotes\ and\ a\ \$

Yes the example in the article and parent comments ought to be referred to as escaping, not quoting. Most of the time, quoting with single quotes leads to something far easier on the eyes.

Here's an example function for quoting from stdin:

    function bashquotesingle() { 
        printf "'"; 
        sed "s/'/'\\\\''/g"; 
        printf "'"; 
    }

Though it does have a bug, at least on macOS, where sed adds a trailing newline. (See https://stackoverflow.com/questions/13325138/why-does-sed-ad...)