Unless expressly forbidden sovereign States can do what they want under international law. There is no prohibition of taking into possession lunar resources once they are extracted in the OST, therefore it must be permitted. The terms of the OST are so vague and open that universal consensus will not likely occur. I concur completely. My comment focused solely on the very ambiguity of which you refer.
Nations can afford to be more tolerant of such ambiguities than corporations can.
Consequently, there is an added importance in any effort to expressly permit ownership of removed resources. I don't think there is any direct, concrete, tangible support for this view in the treaty. Unless expressly forbidden sovereign States can do what they want under international law. There is no prohibition of taking into possession lunar resources once they are extracted in the OST, therefore it must be permitted. The terms of the OST are so vague and open that universal consensus will not likely occur.