Left: co-infall scenario proposed by Donlon & Newberg (2023) for an ancient massive accretion event, together with the qualitative E and L_z distributions such an event would produce. Right: (1) E and L_z distributions of GSE 1 and GSE 2 determined in this work (black edges mark the GSE selection in D23). The histograms show normalized probability density distributions with Gaussian fits overlaid. (2) The bootstrapped [Fe/H] median trends (over 1000 samplings) for GSE 1, GSE 2, and the combined GSE 1+2. Shaded areas indicate the 16th-84th percentile uncertainties from the bootstrap.