You mean, where in htaccess does it go? Doesn't matter. Ordering in htaccess only makes a difference within individual modules. This one's a free-standing directive. Unless you've got something else in htaccess that says "yes! index all you like! override all other instructions!" and it overlaps the js/txt/xml group. This does not seem likely.
They probably use js when constructing Previews. But I can't personally check, because my js tend to involve fonts-- or piwik tracking-- so the default version is the same as the <noscript> version.