again, when building the apk, that asset folder will end up, zipped, inside of the apk.
c-code, like fopen() cannot reach it there (different to java !)
similar problem for nn models, pretrained tracker files, anything you’d just load ‘from disk’ on a pc.
when you compile / build your program, your phone is not present, so no hd / sdcard to put it, that’s why such files end up (temporary) in your ‘assets’ folder in your project