When conferring the sacraments, the minister must have the intention to do what the Church does. One cannot withhold the intention to perform an act that one performs. If the proper matter and form are used and the minister performs the rites according to the rites established by the Church, he is intending to do as the Church does.
The idea that a person can withhold intention for performing an act while actually performing the act is like saying that Mother did not intend to make dinner even though she made dinner and dinner was set on the table.