Wrecks should contribute more to intelligence on enemy classes. If you salvage an engine, gauss turret and thermal sensor from a wreck*, those components should be added to the intelligence report (in addition to mere evidence of a related technologies). Therefore, each wreck could contribute, piece by piece, to the class' design summary. Also, the salvaging of a wreck could have a small chance of revealing the design of its entire class.
*Of course, salvagers would be able to tell if the component was installed on the ship or simply stored in the cargo hold.