[Marcello]

Cluster munitions are lethal weapons, yes. The penetration of a single bomblet isn't impressive by normal standards, around 10-11cm IIRC. However they are released in mid air and will land on a tank from the above. The top turret armor of the typical T-XX is around 4 cm, meaning that it will easily penetrate . Even if the top armor was reinforced (either with ERA bricks or passive armor) the engine deck is still vulnerable, so the tank can still get immobilized.