The fact is that you are testing for viability with an MVP. It is not a product but rather an experiment. You are falling into the trap that most people fall into in thinking it is a product when it isn't. The goal is to validate if there is a demand for your solution, not to create "the product". If you create a whole product then you've defeated the purpose of the lean startup. Look at About.me, they had nothing more than a landing page and got thousands of Beta registrations. The fact is that this approach does work. If the value proposition of the product is attractive to your visitor and solves a large problem of theirs. By creating this basic demonstration to test your assumption you are in fact checking if you would be wasting yours and everyone elses time by building it, that is the underlying premise behind the lean startup.

Also, the post does actually suggest a static prototype as one of the options.