That's true, but it might also be the case that they think this is a good way to work and that's why they built the product in the first place. (I don't agree, though, I think tasks are more suited for DB storage).

Typemill is open source with some paid plugins, I totally agree that a Markdown CMS is not the right solution, but it is an easy way to experiment with new workflows like this. I guess we will see other software in future if tasks will make the journey into the repos.