Anyone also think these kind of posts exist to scrape and create a database of usernames and try to match their real names?

No.

There are a lot of phishing attempts on social media, but this one makes literally no sense. Let's take a look simply at the one post here. u/nightmarepizzza put "aardvark."

So their name is...what? Alex? Amber? Aaron? Abraham? What exactly could ever be discerned from this? Also, we have no idea if they even took it seriously and used the letter of their REAL first name here.

If this were a scam attempt, it would be the worst fucking one imaginable.