Why firing under cloak is exceptional in Star Trek

Can a cloaked Star Trek ship fire its weapons without revealing itself?

Usually weapon fire interferes with cloaking; Chang's Bird-of-Prey and the Scimitar are cited as unusual exceptions.

Firing weapons normally interferes with a Star Trek cloaking device. Chang's Bird-of-Prey can fire torpedoes while concealed, giving it an advantage without establishing that all its weapons work under cloak. The Scimitar has another unusually advanced cloaking system. Both exceptional ships are destroyed, and Chang is said to have kept his device under his own control. Their capabilities cannot therefore be assumed for every cloaked ship.