Related to this question: is it safe to depend on the preview link for the purpose of scheduling social media posts?
At first glance, it appears to work fine to schedule a Facebook or X post using the preview link, prior to the publication of the post, with the social media post scheduled to occur after the post goes live - but will those links break at some point in the future?
Yes, I have noticed that behaviour (preview link redirecting to live link); from your description, it sounds like that can indeed be relied upon, for this use case (scheduling social media post prior to the eventual live link being active).