First, techincally(and technically is called the best kind of correct for a reason), they are a part of the outlands. In actuality they are 90%+ the neighboring plane because of the amount of influence there.
Second, please quote me saying that there is no material on the outer planes, because that's a substantial mischaracterization of what I have said from my first post here. What there is, is not nearly enough to go on. 4 pages on the general outlands, 2 of which cover EIGHTEEN realms, and a bunch of gate towns that while they are technically in the outlands, are mostly the neighboring plane and not the outlands. And I see nothing on the other planes in the table of contents.
Third, False Dichotomies are as usual, false. I reject your "which is it" that so badly mischaracterizes what I've been saying and go with the different option that has been my stance here.