The language is plain in Article IV as it is in Article I.
Article one says what they are allowed to own it for. Artical 4 does not negate that, only says they are allowed to own what the Constitution says they can own. Art 4 is general not specific. Art 1 is specific. Thus Art 1 is one that limits Art 4. To say otherwise negates the plain language of Art 1 specifying what the Federal Government can own land within a state for for.