为什么BinaryReader.ReadInt64（）分别以大/小的形式读取数据？

Question

我对微软的BinaryReader有疑问。

来自https://referencesource.microsoft.com/#mscorlib/system/io/binaryreader.cs，

public virtual long ReadInt64() {
        FillBuffer(8);
        uint lo = (uint)(m_buffer[0] | m_buffer[1] << 8 |
                         m_buffer[2] << 16 | m_buffer[3] << 24);
        uint hi = (uint)(m_buffer[4] | m_buffer[5] << 8 |
                         m_buffer[6] << 16 | m_buffer[7] << 24);
        return (long) ((ulong)hi) << 32 | lo;
}

它将数据解析为Int64数据的两个部分（高32位，低32位）。但我认为这是多余的。所以下面的方法也应该有效。

public virtual long ReadInt64Other() {
        FillBuffer(8);
        return (long)m_buffer[0] | 
               (long)m_buffer[1] << 8 |
               (long)m_buffer[2] << 16 |
               (long)m_buffer[3] << 24 |
               (long)m_buffer[4] << 32 |
               (long)m_buffer[5] << 40 |
               (long)m_buffer[6] << 48 |
               (long)m_buffer[7] << 56;
}

Microsoft有没有理由使用上/下样式解析？