Distribution of the polarisation angle dispersion S and the polarisation fraction p values for the SRoll2 (left panel) and FoCUS (right panel) maps. The data points with error bars represent the mean value and 1 σ dispersion of S within bins of p. The data binning and representation follows that of Fig. 10 of Planck Collaboration XII (2020). The grey line shows the relation S×p = 0.24°, which is expected based on the analytical model of Planck Collaboration XII (2020) for the resolution FWHM = 40′ we used.