Are you asking "Why not spray Copper Oxychloride through the flowering season?" The answer is that sometimes you do.
According to a product application sheet for the fungal spray that Amgrow provides here, for specific fruit trees (like peach) in treating a specific fungal (like Leaf Curl) you do not want to spray past the budding season. In this case it is because you could damage the tree or the fruit.
In other cases it shows that it can be sprayed all the way through harvest (for instance you can for Avocado). This means that applicaiton is not always stopped at the flowering stage.
The chemical name for this product is actually Dicopper chloride trihydroxide, if you want to do more research into the actual chemical.
If this is not what you are asking, I apologize. The question was originally hard to understand - maybe due to a difference in your original language?