I think it is rather opposite - they stripped Debian Linux of non-free packages, added some privacy features - and then hand-tailored hardware to work with it.
Of course it wasn’t pure bottom-up or top-down, rather the mix which met in the middle as end product, but I’m pretty sure the reason it does not work on other laptops is not privacy-related customisation made by purism, but mere removal of non-free components of the debian (which contains firmware blobs). You can try it yourself to make your opinion - eg install debian on system with coreboot and without non-free/contrib (main/security only).