They're different subjects, in my opinion.
Extension 1 looks at ways of thinking - texts, context, ways of analysing texts and ways that texts are constructed (theoretically, not literal construction - that's English adv.)
Extension 2 allows you to gather all you've learnt and apply it to a particular facet which appeals to you. For example, if you enjoy postmodernistic nihilistic tragedy, you could create a postmodern piece which examines, deconstructs, and analyses postmodernistic nihilistic tragic poetry (for example.)
Rather than be taught the theories, you're expected to apply them, in other words.