The old 'shell game' idea, huh? I suppose that would be usable against humans. The AI seems to know what you really have in a given location. At least if people use this strategy the 'Long Range Sensors' start to have real value.
As it is, you learn everything that is in a ship class anytime you get into combat with it. All you have to do is send one little scout in to see the composition of an entire fleet. A small price to pay if you save a flet of deadnoughts from disaster. If the scanner jammer also worked in combat things would be different.