EDIT: Moved to corresponding forum SDK.
By default the data of your snap is not accessible by any other snap on the system. The snaps run in their restrictive security sandbox. To learn more about this you can look at: snapcraft.io - security policy and sandboxing.
What is shown in the post you mentioned, is how to connect to a the configuration storage on the ctrlX OS. This is a place where you can store files, if you explicitly want to share a file with the user or another app on the system.
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