Why is application data of the same application stored in different locations?

I have installed the same application on

  • a device running Android 7.0 (not rooted) and

  • on a tablet running Android 4.4 (root),

but nevetheless I noticed that the application data (databases/files etc) is stored in different locations on each device:

On the tablet device the files are located at: /storage/sdcard0/Android/data/com.packagename and can be easily manipulated (i.e copy, back up etc) but not on the smartphone which likely leaves the storage location being: /data/data/com.packagename which I have no access to.

I understand that it is usually stored on /data/data (protected internal app storage) or /storage/sdcard0/Android/data (storage on user’s internal storage partition), else on a SD card if present. In addition, a related question has been asked here: Where Android apps store data?

My biggest surprise is why is this happening on the same application (same version – sideloaded)?

This reference page also explains how a developer can configure the default location of application data. It would have been understandable if there were different versions of the application, but here I am only dealing with the same application (i.e .apk file). Is there something I am missing here or things have changed in recent versions of Android?

My concern is that I can’t access these files on /data/data without root and since these are large files and I need to back them up just in case the app data is accidentally cleared (and I have already done that by mistake :(.

Most importantly I don’t want to continuously download them over again.

Note: Both devices have no external storage attached.

From the look of things the biggest obstacle is not being able to access files on /data/data (device 1), hence no backup possible…(I would appreciate if there is another reliable workaround to achieve this)