You're thinking too much. The FSF isn't a religious organization. It's not a
sin to use hardware that mistreats you. The FSF only gives the best
recommendations it can.
The "Respects Your Freedom" page lists hardware which has no proprietary
firmware requirements, with the exception of firmware that is burnt onto a
ROM and embedded into the hardware itself (such as the firmware in the hard
drive and the firmware in the keyboard).
The "companies that sell computers pre-installed with GNU/Linux" page is just
that: a list of companies that offer the option to buy their computers
pre-installed with an FSF-endorsed GNU/Linux distro. This does not mean that
the computer has no proprietary software. But after RYF-endorsed devices,
this is the second-best choice. (Think Penguin, in particular, makes an
effort to ensure that all of its hardware works out-of-the-box with
Linux-libre.)
The list of single-board computers gives information on single-board
computers available, i.e. what flaws each of them has.
There is no such thing today as "free hardware". All hardware manufactured
today includes components sourced from one of a few very large corporations;
this is currently an economic necessity. Designs for these components are not
available. There isn't even a such a thing as a computer that includes
absolutely no proprietary software, since as I alluded to earlier all of them
have embedded firmware in things like keyboards and hard drives. Heck, every
single USB device you use has some sort of firmware embedded into it, and
this is proprietary firmware. That's why the FSF makes an exception for
embedded firmware; a device running only libre software in every component
just isn't feasible, at least not today.
