AmbiguousMatchException When Binding To Default Property In WPF

The following XAML produces an AmbiguousMatchException. The DataContext for myText is a DataTable consisting of > 1 row which contains a DataColumn named "test":

<TextBox Name="myText" Text="{Binding Path=Rows[0].Item[test]}"/>

When I modify the binding path syntax to the below example, the binding works as expected:

<TextBox Name="myText" Text="{Binding Path=Rows[0][test]}"/>

Given that the name of the DataTable is "myData", both of the following lines of code reference the contents of the column "test" on row 0:

myData.Rows(0)("test")
myData.Rows(0).Item("test")

Why doesn't the syntax that explicitly names the Item property appear to work in a binding scenario?