Not cheating, but being a four letter word, yes.
I would say a*hole if it was casual play. But tournement, you better know your ships and abilities.
Yeah, I could see that in a tourney, but I would still let him cloak. Who is not going to cloak w/ ACD after they fire? Its almost an automatic thing for me. I even let people do an action if they forgot it after they moved, but before the activiation phase officially ends. Now if we are in the combat phase and he's like "I would have focused with such and such." I tend to draw the line and say better do it next time.