The main reason the GPL exists was to insure changes to code (forks) were available to original developers of the code so they could include those changes if they wanted (this was a result of issues with earlier unix systems that had fragmentation from forks). Additional, Linus, author of Linux, has been clear that his focus is getting code back, what happens to hardware was not covered in his mind by GPLv2.
So there is a dispute as to what GPLv2 requires with respect to hardware. It's clear that the code must be shared, and that's what a lot of GPLv2 devs have focused on. That the source code be shared, including scripts used for compilation and installation.
But (one view) is that is separate from mandating behavior of hardware, and that hardware can still check if its running approved code and refuse to run if approved code is not loaded.
That's why this case is so huge. The actual developers of Linux are not likely to try to enforce a term they don't think exists, the SFC very well may.