Really what they are doing is showing that the Bible teaches a 6000 year-old Earth no more definitively than it teaches a flat one and pointing out that hypocrisy to creationists. Being able to make fun of flat-Earthers is a sport all can enjoy.
For a person to insist on the 6k yr old earth is every bit as
ludicrous as flat earth.
It is far easier to show the earth is round,
very difficult to deny the obvious evidence.
Showing the earth is ancient and there
was no flood is more involved but no less clear.
We had a maid who thought the earth is flat.
It was such fun to see her struggle with it and
then, epiphany! She got it!
Of course, she came from rural third world
where they be believe it's a lizard trying to eat the
moon that causes eclipse.
Americans generally have less excuse,
though educational and cognitive handicaps
limit some, while others who have the capacity
to do better choose to go the used car salesman
route, and surrender integrity to expedience.