The current cosmological dark sector (dark matter plus dark energy) is challenging our comprehension about the physical processes taking place in the Universe. Recently, some authors tried to falsify the basic underlying assumptions of such dark matter–dark energy paradigm. In this Letter, we show that oversimplifications of the measurement process may produce false positives to any consistency test based on the globally homogeneous and isotropic Λ cold dark matter (ΛCDM) model and its expansion history based on distance measurements. In particular, when local inhomogeneity effects due to clumped matter or voids are taken into account, an apparent violation of the basic assumptions (‘Copernican Principle’) seems to be present. Conversely, the amplitude of the deviations also probes the degree of reliability underlying the phenomenological Dyer–Roeder procedure by confronting its predictions with the accuracy of the weak lensing approach. Finally, a new method is devised to reconstruct the effects of the inhomogeneities in a ΛCDM model, and some suggestions of how to distinguish between clumpiness (or void) effects from different cosmologies are discussed.