A wetting agent is not the same as a moisture retaining granule.
The wetting agent is a type of detergent to make it easier to have peat, and to a lesser extent coir or bark, take up water after they have been baked dry. Without it, the water just runs straight through or pools on top. So nothing wrong with the wetting agent itself, except that it indicates the bag has the wrong sort of stuff in it
Moisture retaining granules suck up relatively large amounts of water and then release it slowly as the surrounding soil dries out. They expand into gel-like lumps when they are full of water. They aren't as bad as they sound for cacti, because they store the water in a way that doesn't promote rot. They can keep extremely free-draining soils moist for a little longer and give plants a chance to get a drink without ever having to be in a soggy soil. However, a soggy soil plus water retaining granules is a disaster because they will keep the soil soggy for longer. The fired clay granules that many people use do a similar job, but they don't store as much water.