Is there a purpose to this _com_ptr_t move assignment?

So we have this code

_com_ptr_t& operator=(_com_ptr_t&& cp) throw()
{
    if (m_pInterface != cp.m_pInterface) {
        Interface* pOldInterface = m_pInterface;

        m_pInterface = cp.m_pInterface;
        cp.m_pInterface = nullptr;

        if (pOldInterface != nullptr) {
            pOldInterface->Release();
        }
    }

    return *this;
}

The pOldInterface is Release()d on move assignment. Why are move assignment/constructor operations not implemented as swaps which lets the Release() occur naturally on moved object's destruct or just use the nullptr assignment or Release() to manually trigger it early?

I always implement move constructors as swap operations. Is this bad practice?

My code would be

_com_ptr_t& operator=(_com_ptr_t&& cp) throw()
{
    if (m_pInterface != cp.m_pInterface) {
        Interface* pOldInterface = m_pInterface;
        m_pInterface = cp.m_pInterface;
        cp.m_pInterface = pOldInterface;
        // or just std::swap(m_pInterface, cp.m_pInterface);
    }
    return *this;
}

Is there a reasoning behind MS _com_ptr_t choice? This question also applies to any move assignment/constructor so this context is more/less relevant. It's all about whether we release data or we swap it?