Seeding can increase the size of a storm.
Condensation is exothermic and exothermic reactions give off heat energy. Seeding the air to increase condensation increases the amount of energy in one location which then pulls from other locations, enhancing the size and potential of a storm.
Yes, condensation is exothermic, but you way overestimate the amount of heat released, where in the atmosphere the heat is released, and its effects on water evaporation at the surface necessary to form clouds.
Cloud seeding works by providing a nucleation point for a water droplet to form, but the initial water vapor must be present. The effects are local to where the seeding is done, and is only successful if the amount of moisture in the cloud is almost enough for it to rain naturally.
Look at the radar again, and tell me that a storm nearly the size of the Arabian Peninsula was caused by cloud seeding.