There are things intentionally included and things intentionally excluded from the sandbox. App-specific data storage is part of the former, and external storage access is part of the latter (this changed with Android 10, anyhow).
Epic's installer used the external storage
There are things intentionally included and things intentionally excluded from the sandbox. App-specific data storage is part of the former, and external storage access is part of the latter (this changed with Android 10, anyhow).
Epic's installer used the external storage