Part of the problem is terminology, the pool industry as a whole has misused both the term shock and oxidizer (more so with shock) so much that it is hard to know what people are actually referring to when they use those terms, around here we teach a proper understanding of the effects and side effects of pool chemicals, we therefore try to refer to them by there chemical names or at least the short version of those chemical names. In the pool industry the term shock when applying to a product can mean any of about 5 or 6 chemicals, primarily liquid chlorine / bleach, dichlor, trichlor, cal-hypo, lithium-hypo, or even MPS (chlorine free shock), each one having different secondary effects that may be good or bad depending on the chemical balance of your pool.