Cannot use the same template arguments on function as the ones on struct

[MrSmith via Digitalmars-d-learn]

Here I have templated struct that matches type with CborConfig 
tempate specialization

CborConfig will have more parameters in future and all of them 
will be accessed via alias members, so I've used variadic (T...) 
parameter whule matching.

-------
template CborConfig(_nonSerializedAttribute)
{
        struct CborConfig
        {
                alias nonSerializedAttribute = _nonSerializedAttribute;
        }
}

/// Default non-serialized attribute type
struct NonSerialized{}

/// This CborConfig instantiation will be used by default.
alias defaultCborConfig = CborConfig!(NonSerialized, 
NonSerialized);

struct AccepterT(Config : CborConfig!(T) = defaultCborConfig, 
T...)
{
        pragma(msg, T);
}

// template f379.accepter cannot deduce function from argument 
types !()()
void accepter(Config : CborConfig!(T) = defaultCborConfig, T...)()
{
        pragma(msg, T);
}
-------
^^^^^^^
http://dpaste.dzfl.pl/5f1d5d5d9e19

Instead I need to use template constraint which is less compact.
http://dpaste.dzfl.pl/571ae84d783e

Why such behavior happens?