Admins can see all old versions of edited posts.
A better way of framing someone would be to use an external site under your control, and fake the creation date of a post.
This has happened.
Is it the case from which bitcointalk.org forum has feature to see edited time of post/ thread? I checked the
topic, but did not see such information on the activation day of Edited time Display. In my experience, I saw Edited time on my mobile devices just recent months, maybe in the early days of 2019, not in 2018. It is easy to realize on mobile devices because Edited time automatically displayed. On computer or laptop, we have to scroll mouse to the line of Publishing time to see Edited time.