Tracks of type-I candidates (sample S₀) in the E_p,i − E_iso plane as a function of z. The tracks are colour-coded according to their ℒ_* values, with darker (lighter) colours corresponding to higher (lower) ℒ_*. Blue and brown points represent GRBs from sample S_I and S_II, respectively. The red line shows the E_p,i − E_iso relation and the shaded areas are the 1-, 2-, and 3-σ_int regions. The gold star is GRB 230307A.