Agreeing here. There are times where Illo notes can be needed for both Agent/Editor and Illustrator but they are usually few and far between. They would be necessary if, for example, the text said "June was just SOooooo excited about dressing up for the party" and the intention is sarcasm, you mean for June to look furious about having to dress up.
In your example about the gifts though, if the Illustrator is struggling to come up with enough idea's for what items to draw, he/she can consult with the Art Director for suggestions.