As mentioned by many people, open source gives you peer review as an advantages, and bugs (both in-good-faith and intentional) get more easily spotted.

This however doesn't prevents bug from be there, and the question is: will those guys be keeping their custom systems up to date?

Also, as you point out, a lot of the work is now moved on this [gorram] cloud, and unfortunately the simple fact you're running GNU/Linux hardly prevents information from leaking. I wonder if they will also be using strong cryptography or custom online services!

EDIT: the distro is likely being a spin-off of something existing -- indeed, https://en.wikipedia.org/wiki/GendBuntu as somebody linked -- so yes, that will be up to date.