Bootstrap provides a slim set of tools for constructing a website. The power comes in it's components, mobile-readiness, and extensibility. Going from default Bootstrap to either of these two sites would still take a lot of design work. You can also see the linked article's author talking about specific design decisions they made that aren't made by default Bootstrap.

I think a more accurate critique would be to look at some of the templates on Wrap Bootstrap. A lot of them do similar things to both of these websites.

This. Kintek was clearly inspired by what Infinum did, especially on some of the graphical elements.

But they both appear, on a code level, to be Twitter Bootstrap. Infinum definitely needs to get over themselves.

And why is that a problem? Isn't the whole idea of bootstrap to serve as a starting point?

Yea this is a very common design pattern.