There's a big difference between information about the programming interface of a device, and "blue prints" that would allow a competitor to easily implement a copy. It might make it easier to produce hardware that works with the same drivers, but probably not easier than just writing new drivers for totally unrelated hardware (unlike in the DOS days where drivers were embedded in application code, and hardware compatibility was the only reliable approach).
There is lots of hardware with open source drivers -- how often does that result in the hardware being cloned?
Of course, some devices are relatively simple things with all the intelligence in the driver software. In that case, you'd have more of a point (though you could still document the interface to the hardware itself), but that's more about selling software than preventing a clone of the simple hardware. It doesn't justify a general statement that Linux driver development is "pure hell".