I think that in the simplistic picture-yes omission is lying.
Thus the expression, "lying by omission" and "the truth, the whole truth and nothing but the truth".
I used to think that omission was ok for certain reasons.
I don't any more.
Now I think that TIMING is crucial, but honesty needs to be complete.
That said-I don't tell Maca details about my sexlife with GG because he doesn't want to know them. But if he asks-I ALWAYS tell him the complete truth. The only reason I don't offer it is because he has requested specifically that I do not.
There is a difference between someone asking you to "spare me the details" and you deciding to spare them the details yourself. I think the first is fine-the second is dangerous for relationships.
"Love As Thou Wilt"