Memory cache dependencies

I'm trying to understand the Cache dependencies example, but some of it is eluding me.

var cts = new CancellationTokenSource();
_cache.Set(CacheKeys.DependentCTS, cts);

using (var entry = _cache.CreateEntry(CacheKeys.Parent))
{
    // expire this entry if the dependant entry expires.
    entry.Value = DateTime.Now;
    entry.RegisterPostEvictionCallback(DependentEvictionCallback, this);

    _cache.Set(CacheKeys.Child,
        DateTime.Now,
        new CancellationChangeToken(cts.Token));
}

CancellationTokenSource allows evicting multiple cache entries as a group. But what's the point of the using block in this example? I downloaded the sample project and replaced the using block with the following:

_cache.Set( CacheKeys.Parent, DateTime.Now, new CancellationChangeToken( cts.Token ) );
_cache.Set( CacheKeys.Child, DateTime.Now, new CancellationChangeToken( cts.Token ) );

While my two lines are simpler, they seem to have the same effect as the using block. The doc says:

With the using pattern in the code above, cache entries created inside the using block will inherit triggers and expiration settings.

What does "triggers and expiration settings" refer to here?

I must add dependent cache entries in my application, but they must be added at separate times. Therefore I can't take the approach shown in the example's using block since it requires both entries be added at the same time, right? What functionality am I missing out on by instead taking the approach shown above in my two lines of code?

Finally, shouldn't Dispose be called on CancellationTokenSource after the Cancel call? The sample doesn't do that.