Yes newly published hosted feature services generated after the last AGOL update will run through this storage model. This info was also included in the AGOL update email "Whats New" for the July release and in the Whats new release notes under the AGOL docs.
- Email notes
Under the Services section
We are providing file-based storage for attachments in hosted features layers. Attachments included in hosted feature layers are stored as files instead of features, reducing your organization’s credit costs for storing feature services. "
-Doc notes
Under Hosted Features and Tiles section
Attachments added to hosted feature layers after July 2, 2014, are now stored as files, reducing storage costs for your organization.