Below is a comprehensive brochure outlining the acoustic qualities of the loose lay vinyl planks. You may find it useful as a reference.
It appears that there are ways to make this type of flooring perform better by way of an installation of a Regupol acoustic underlay. The thickness of the underlay can be either 3 mm or 4.5 mm.
Impact sound must be 62dB or less for multi-residential applications in accordance with standard ISO 717 – 2.
Apparently the loose lay planks are 62dB or 61dB with no underlay (depending on the thickness of the slab). This improves to 57dB and 55dB with the 4.5 mm underlay.