Why ContentResolver does not see added files by another app?

I added files to Documents/MyExcelsFolder by using ContentResolver.insert and then also added new file to Documents/MyExcelsFolder folder by another app (for ex. FileManager)

Then I try to get all files from the MyExcelsFolder folder

fun getAppFiles(context: Context): List<AppFile> {
        val appFiles = mutableListOf<AppFile>()

        val contentResolver = context.contentResolver
        val columns = mutableListOf(
            MediaStore.Images.Media._ID,
            MediaStore.Images.Media.DATA,
            MediaStore.Images.Media.DATE_ADDED,
            MediaStore.Images.Media.DISPLAY_NAME,
            MediaStore.Images.Media.MIME_TYPE
        ).apply {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                add(
                    MediaStore.MediaColumns.RELATIVE_PATH
                )
            }
        }.toTypedArray()
        val extensions = listOf("xls", "xlsx")
        val mimes = extensions.map { MimeTypeMap.getSingleton().getMimeTypeFromExtension(it) }

        val selection = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            "${MediaStore.MediaColumns.RELATIVE_PATH} LIKE ?"
        } else {
            "${MediaStore.Images.Media.DATA} LIKE ?"
        }

        val selectionArgs = arrayOf(
            "%${Environment.DIRECTORY_DOCUMENTS}/MyExcelsFolder%"
        )

        contentResolver.query(
            MediaStore.Files.getContentUri("external"),
            columns,
            selection,
            selectionArgs,
            MediaStore.Files.FileColumns.DATE_ADDED + " DESC"
        )?.use { cursor ->
            while (cursor.moveToNext()) {
                val pathColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA)
                val mimeColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE)
                val filePath = cursor.getString(pathColumnIndex)
                val mimeType = cursor.getString(mimeColumnIndex)
                if (mimeType != null && mimes.contains(mimeType)) {
                    // handle cursor
                    appFiles.add(cursor.toAppFile())
                } else {
                    // need to check extension, because the Mime Type is null
                    val extension = File(filePath).extension
                    if (extensions.contains(extension)) {
                        // handle cursor
                        appFiles.add(cursor.toAppFile())
                    }
                }
            }
        }

        return appFiles
    }

fun Cursor.toAppFile(): AppFile {
    val cursor = this

    val idColumnIndex = cursor.getColumnIndex(MediaStore.Images.ImageColumns._ID)
    val nameColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME)
    val mimeColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE)
    val pathColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA)

    val id = cursor.getLong(idColumnIndex)
    val uri = ContentUris.withAppendedId(MediaStore.Files.getContentUri("external"), id)
    val fileDisplayName = cursor.getString(nameColumnIndex)
    val filePath = cursor.getString(pathColumnIndex)
    var mimeType = cursor.getString(mimeColumnIndex)
    val relativePath = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        cursor.getString(cursor.getColumnIndex(MediaStore.MediaColumns.RELATIVE_PATH))
    } else {
        null
    }
    var type = MimeTypeMap.getSingleton().getExtensionFromMimeType(mimeType)
    if (type == null) {
        type = File(filePath).extension
        mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(type)
    }
    return AppFile(
        id = id,
        uri = uri,
        absolutePath = filePath,
        name = fileDisplayName,
        mimeType = mimeType,
        extension = type,
        relativePath = relativePath
    )
}

And in result there are only files from ContentResolver added by insert command, and there no files copied by FileManager. How to see all files in cursor?

Operation system: Android 10 (Q) (API level 29)

Target API version: api 29

from Why ContentResolver does not see added files by another app?