Opening the disconnect will not remove the 120 VAC that is provided by the IO module.
Technically, this may not be an NEC violation any more than the presence of 2 voltage sources in any single enclosure, in this case, the peckerhead. However, most electricians probably would assume that if the disconnect is open, there is no voltage present.
At the very minimum, a warning that more than one voltage source is present should be posted somewhere.
