A 2008 study found that three commonly used measures of cognitive load responded differently to intrinsic, extraneous and germane load, and researchers have separately proposed an additivity hypothesis under which the three load types overlap substantially rather than staying cleanly distinct, so the theory's own three-way split has not been settled as measurably separable.
What would resolve this Converging physiological, behavioral and self-report measures of cognitive load that agree with one another across instructional conditions designed to isolate each load type in turn.
OpenEducational psychology and psychometricsWikipedia: Cognitive Load