Real Property, Tenant's rights, and Landlord laws are an entirely separate domain. However, I believe in some places if you stop paying rent long enough, then yes all your stuff now belongs to the landlord because they have the "key".

"the data they already have" means the data the user gave the company (no one is "giving" their files to their landlord) and that the company is in full possession of and now owns. Users in this case are not in possession or ownership of the data they gave away at this point.

If you hand out photocopies of the files in your apartment, the files in your apartment are still yours, but the copies you gave away to a bunch of companies are not. Those now belong to the company you gave them to and they can do whatever they want with it. So if they keep it and a judge tells them the documents are not to be destroyed (because laws things), they would probably get into trouble if they went against the order.

Which is what I was trying to bring attention to; the fact that the company has a choice in what data (if any) they decided to collect, possess, and own. If they never collected/stored it then no one's privacy would be threatened.