From what I've seen, there's actually two different levels of free tier. There's the one where you make an account and don't give them your payment info, and are on a free trial (availability of Ampere servers is severely limited in this, and they deactivate your account if you don't sign in often enough or use the servers you create), and the other where you give them payment information and set up a real account and get credits towards 200GB storage and the free tier compute.
My guess is that people who complain about their stuff being deleted are on the former.
When signing up for free tier the first month is actually a trial. After 30 days trial ends and you are downgraded to free tier. That causes the VMs to be destroyed. BUT! The storage with data stays and you simply recreate the VMs attach the disks and and everything continues to work.
Another possibility is that Oracle wants the machines to be used. So a simple `stress -c 1` in a screen is enough.
My guess is that people who complain about their stuff being deleted are on the former.