Are you suggesting the FO shouldn't be adjusting radios and Navaids without running it past the captain first?
Some times it's a good idea. A mate was passing about 2000' on an ILS, in the gloop, when the ILS display in the Boeing failed.
Unbeknown to him, F/O Bloggs had decided it would be a good idea to detune the ILS in favour of the VOR, and did it saying nothing until after the apparent failure.