Distribution of relative escape fraction (f_{esc,  rel}(LyC)) for GRB 050908, GRB 060607A and GRB 191004B (from left to right) with and without uncertainty on the observed measure of (f₁₅₀₀/f₉₀₀)^obs from the afterglow spectrum (respectively gray and black distribution). The high values with f_{esc,  rel}(LyC) > 1 are non-physical and due to low IGM transmission, hence we restrict the statistics and axis range to 0−1 for f_esc, rel(LyC). For GRB 191004B, 57% of the gray distribution is at f_esc, rel(LyC)≤1 while the fraction is 92% and 96% for GRB 050908 and GRB 060607A, respectively. The solid red and orange lines in each panel represent the median and average value of this f_esc, rel(LyC)≤1 part of the distribution. The dashed red lines represent the corresponding 16th and 84th percentiles. The f_{esc,  abs} are similar to the values quoted here for GRB 050908 due to the null extinction hypothesis. For GRB 191004B and GRB 060607A the corresponding absolute values are derived in Sects. 4.2 and 5.