Different ways to destructing unique_ptr

I analyze a class with unique_ptr member. That member may be used from different threads. There is also a method which destroys that member:

void uninitialize()
{
    std::unique_ptr<Worker> worker;
    {
        std::lock_guard<std::mutex> guard(mtx_);
        worker = std::move(worker_);
    }
}

I wonder what is purpose of that impl. Is there any difference between the above and the following implementation? :

void uninitialize()
{ 
    std::lock_guard<std::mutex> guard(mtx_);
    worker_.reset();
}