it's that in the GBA case it's the ONLY user documentation for that feature. I am fucking not going to remember 2 years from now when someone asks how to change the light level in Boktai that you need to look that up in the 0.175 whatsnew, and neither are any of you. We need to get per-system documentation going on the website pronto and start including this sort of thing there.
As it has been already clarified elsewhere, it was never intended to be the *ONLY* user documentation.
It is like that so far just because Firehawke is still working on the general documentation and I don't want to interfere in any way in his great job.
Once he's done or he declares the time has come for multi-contributor handling, I will make sure that the info is added also in the per-system documentation.