Omari,Hi Oxwall Tips, I can confirm that this is not true, a plugin needs to be be specifically configured to use amazon s3 cloud support.
https://wiki.oxwall.com/install:cloud_hosting:amazons3
This is base config, therefore will work for any plugin that stores data in ow_userfiles directory.
However what you can do is use any 3rd party plugin (not a default one) that stores user files; and check the file storage location with cloud support enabled.
You will find that the file is stored in the sitename/ow_userfiles directory and not on Amazon.
Let me know you thoughts.
I have carried out the actions to use Amazon s3 and it functioned, but with problems. The header changed and wouldn't accept a new photo. Also it did not use the amended css. I gave up using it.