Short answer: every creative stays linked to its source post — but serves as a fully independent ad.
The living link
The creative's overview shows the source handle and links to the original post.
Engagement counters (likes, comments, views) render on the unit from the source post's real data — that's the social proof doing the work.
Posts stay synced from the brand's connected handles, and creatives on a refresh tier (e.g. hourly) pick up updated counters without re-trafficking.
The independence
The unit itself is a standard ad: it serves from your ad server, and every interaction goes to your click-through destination — not to the social network. (Social exit elements are off by default in 2.0 — see How does a user interact with the unit?)
Related