Flux and spectral evolution of GRB 180128A (lavender), GRB 200415A (orange), and GRB 150101B (amber). Left (a): correlation between L_iso and E_p for all three transients, revealing an approximate $L_{\mathrm{iso}}\propto E_{\mathrm{p}}^2$ relationship that is a strong signature of relativistic winds. The temporal binning for panel (a) is uniformly 8 ms and uses the values in Table A.1. Right (b):L_iso and E_p for all three transients over the BB intervals in Table 1, omitting the data gaps and saturated intervals of GRB 200415A. All fit errors and error bars are at the 1σ confidence level.