Recently, Picardi and coworkers emphasized the physical difference between the kinetic-Abraham and canonical-Minkowski quantities, arguing that "the former ones describe the properties of "electromagnetic fields only", while the latter ones characterize properties of the "whole wave mode" (i.e., a polariton, which involves, on the microscopic level, oscillations of both fields and electrons in matter)". However the EM fields can be divided into two kinds: radiation field (made up of photons) and non-radiation field (such as the self-field carried by a charged particle). Picardi and coworkers did not explain whether or not the "electromagnetic fields only" include the non-radiation field carried by "electrons in matter", thus leading to an ambiguous implication.