I think you are missing the forest through the trees. The point is that there is significant computational power inside your old smartphone, which could be used for many different things. The bitcoin mining is simply illustrating this and showing how it is more computationally efficient than a desktop/labtop.

I was thinking the same thing. The lack of details on mining speed tends to support that as well. It just looks like they built a technically interesting toy and used "bitcoin" as a way to get it some attention.