Ratios of $v_2/\varepsilon_2$ as a function of $(1/S)\dNchdEta$ in \XeXe (top panel) and \PbPb (middle panel) collisions The Linear fit functions to $v_2/\varepsilon_2$ in the top and middle panels are shown by lines The bands show the uncertainty of the fit (bottom panel) The ratio of $v_2/\varepsilon_2$ to the linear \PbPb fits shown in the middle panel The data points of \vtetagap, \vtf are shifted by $-0.1$ and $+0.1$ along $(1/S)\dNchdEta$ for better visibility The error bars (open boxes) indicate statistical (systematic) uncertainties The ZDC scale uncertainty, due to residual correlations in the determination of the denominators in~\cref{eq:v2spe}, and the bin-to-bin uncorrelated one are combined for \vtsp (top and middle panels) For the ratio of \vtsp to the \PbPb fit (bottom panel), the ZDC scale uncertainty is separated and is shown by the solid boxes on the left side of the bottom panel The grey box at unity in the bottom panel on the left side shows the variation depending on the \TRENTo configuration The blue horizontal band (bottom panel) represents the relative uncertainties of the individual linear fits to the \PbPb data from the middle panel The red horizontal line (bottom panel) shows a combined fit of a constant function to the \XeXe data and its uncertainty.