5. Extract duplicated code - alternative solution rejected

[rwst]

In the "5. Extract duplicated code" task, submitting this solution fails:

...
fun wordCount(fileName: String): Int {
    val file = checkFile(fileName)
    var wordCount = 0
    file.forEachLine { line ->
        wordCount += line.split("\\s+".toRegex()).count()
    }
    return wordCount
}

private fun checkFile(fileName: String): File {
    val file = File(fileName)
    if (!file.exists() || !file.isFile) {
        throw FileNotFoundException()
    }
    return file
}

fun copyFile(srcName: String, destName: String) {
    val file = checkFile(srcName)
    val to = File(destName)
    file.copyTo(to)
}

While the err message states: Please, extract the code that checks if the file exists and is valid. I think this solution should also be accepted, or, if you reject the suggestion then, at least, that sentence should be shown in the task description.