I do not think there was any concerted effort, in any case I am not aware of any recent discussion on this subject. It is arguably not really needed to concert such an effort (but see below) as the close-review queue handles this nicely and is designed to do this.
If a user decides to look through old content and vote on it, then the their close and reopen votes will become known to others via the review-queues and depending on the opinion of others the vote will either take effect or eventually it will be discarded.
In my mind the main question is do we collectively agree now that the question that were put "on hold" now, would and should be put "on hold" when asked now
If the answer is "no" (for some or all of them) then we can and should undo the closures and those that cast the votes should ideally take this feedback of the larger community on board.
If the answer is "yes" then however I do think quite strongly that it is a good thing to put these questions "on hold." In principle, the current policies apply to the entirety of the existing content and ideally this is reflected in the status of posts.
Of course, there are practical limitations to this and it might make sense to be slightly more lenient with long existing content, but really just slightly.
A reason why I think that it is relevant to curate the old content is that new users might well start out on the site with seeing old content and what they see informs what they think is appropriate (now).
In any case I think we should focus on whether the closures seem intrinsically appropriate now. To have all kinds of extrinsic parameters to consider, like the year a post was created, is not desirable.
While I said above that there is no need to concert such activities, I still would recommend not to start out too intensely with something like this, but maybe just with one or two questions a day, and to see how things evolve.