Thanks for your question 😀.
Always excited to answer! FFiles is not an alternative to storage services Google and Apple provides. It is a "link" based platform to help you send and receive stuff more easily. Kind of like WeTransfer or DropBox. Or Airdrop for Internet.

There is no catch.... it's a paid subscription based service for people who deal with sharing files alot. The developer has no access to your files unless you make it public and choose to share.

It's similar to saying oh Apple's iCloud has all my photos, no privacy..