...the Augsburg confession didn't have a thing to say about it.
Nor should it. Scripture alone establishes articles of faith. A congregation of Christians may have a pious opinion that "This do" requires the sole use of fermented grape wine and unleavened wheat bread based on the historical context of the supper. Another church may have a pious opinion that grape juice and leavened bread are permitted. There is no requirement in scripture that sacramental ceremonies must be completely uniform among all churches.
