Pragmatism pulls in the non-security direction. When security people see "Linux-based", they already know the thing is situated at some particular point on the scale, or worse. Linux has big TCB surface, so it's intrinsically hard to secure.
Sure, one can roll on the ground hoping to get to a slightly higher place ("making Linux more secure"), or one can dig a hole, put up a foundation (L4, Genode, etc. etc.) and build a tower on it. Rolling on the floor is sure easier and provides a sensation of movement ("yay, we have something 'practical', another Linux-based distro! look, we've spent a lot of effort and careful direction planning to roll a few cm/inches higher!"). But as for "realism", which is more realistic: to roll on the ground hoping to get higher, or to build something more difficult which can really get one higher? If I see "Linux-based secure OS", I think of the rolling, and think "right, they maybe got a bit higher, hope they didn't break something unexpected by virtue of spaghetti interactions and actually fell into a hole"; also, there's most probably still a lot of bugs in Linux kernel they didn't know of so couldn't secure. So maybe they even didn't get that much higher they thought they did. But even assuming they really improved a bit and didn't break nothing, they sure didn't get to a tower height.
