Historically all deployed applications in our cloud used local filesystem to store literally a directory with files. About 6 months ago we added support for S3-compatible storage (AWS, Google Cloud Storage and etc) for generated backend applications.
While since the introduction of S3 all new deployments used S3 buckets by default, old deployments continue to use local filesystem. In the next 4-6 weeks we will automatically move all files from local filesystem to S3 buckets for all existing deployments.
We don’t expect any impact to the publication process, except a one-time delay during publication to migrate data.