PhpSpreadsheet won't read 3A Sensitive Data from Excel Spreadsheet

Question

When a user uploads an Excel spreadsheet that's marked as 3A Sensitive (see below), PHPSpreadsheet will say it has zero sheets and returns an empty array when asked for sheet names. How can I get PHPSpreadsheet to read a spreadsheet that is marked as sensitive?

Excel version: Microsoft® Excel® for Microsoft 365 MSO (Version 2308 Build 16.0.16731.20182) 64-bit

    $reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReaderForFile($file_path);
    $reader->setReadDataOnly(true);
    $spreadsheet = $reader->load($file_path);

    var_dump($spreadsheet->getSheetCount());
    var_dump($spreadsheet->getSheetNames());

    exit;