The time-dependent fluorescence depolarization decays of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in the ordered and isotropic phase of a columnar liquid crystal formed by bowl-shaped metacyclophane cores symmetrically substituted by twelve alkanoyloxy chains have been recorded at various temperatures and analyzed using the global target approach. The measurements in the mesophase can be successfully analyzed only assuming a microscopic inhomogeneity of the columnar phase, with the probe partitioned between two environments, i.e. polar cores and apolar aliphatic chains, showing very different ordering and dynamical characteristics. This behavior becomes evident only when all the fluorescence intensities, corresponding to different parallel and perpendicular orientations of the excitation and observation polarizers, are analyzed simultaneously. The picture emerging from the analysis supports other recent findings on this class of columnar systems.