Hello Robert – You are correct, "decoupling" implies totally separating two systems. The proper term would probably be “damping” but this is one of those industry slang issues. Decoupling is commonly used in the soundproofing and audio products industries and has been adopted by manufacturers, industry spokespeople, and audiophiles on these forums.
Damping indicates the dissipation of vibrational energy, implying some portion of the energy entering a system is absorbed and ultimately changed to another form of energy such as heat, resulting in a reduction of the vibrational energy transmitted between the two systems. This more accurately describes what happens when elastomeric materials are used between speakers and the floor. The term "isolation" is sometimes used when referring to mass-loaded spring damping systems. These types of vibration dissipation systems are prevalent in the automotive and machine industries.
As with many things related to this audio hobby, decades of point-proving and arguing have not determined a clear “winner.” Audiophiles are inundated by manufacturers clamoring about how their products are “the best” and frequently using pseudo-science and marketing psychology to influence purchasing decisions. At some point, all arguing aside, it comes down to a comment I recently read on a different thread, to paraphrase, “buy and listen to what you like.”