Here. My quick gloss on my own argument (which Atheology nicely tries to sketch out), without going to the specific passages in Meillassoux’s After Finitude, is that Meillassoux moves from the contingency of the absolute that is the correlation, to the contingency of every entity, from one page to the next. That was the move I was considering, and there was no argument in the text that showed why one should move from a particular relation (the correlation of subject and world) to every entity. In any case, as Atheology notes, this is a side point in the overall argument of the paper.
Now it could be the case that Meillassoux accepts the premise of the correlationist (as depicted by him) that the only absolute is the correlation, and then he thus can say the only absolute is the correlation, which in turn is absolutely contingent. All well and good. But then he still has no warrant for a description of every entity, either ontologically (moving from the relation to the existence of what is not of that relation) or epistemically (since on his account knowledge of these all entities is all but ruled out of bounds by correlationists).
In any case, that’s my thinking on a couple of pages I don’t have in front of me and haven’t looked at in a while–happy to be corrected.