Reproduction of stellar halo flattening q_star as a function of radius R_gc for models with different underlying DM halos. The three panels from left to right are Auriga 23, 5, and 12. The DM halo shapes of Auriga 23 show little variation within our data coverage. The q_star(r) is well reproduced by a model with constant p_DM and q_DM close to the ground truth. Auriga 5 shows mild variation, and Auriga 12 shows relatively strong variation of the DM halo shape, from r ~ 10 kpc to r ~ 50 kpc. Especially for Auriga 12, the stellar-halo flattening, q_star(r), at all regions can hardly be reproduced by a model with constant p_DM and q_DM; in contrast, it can be reproduced well by a model with p_DM(r) and q_DM(r), which vary with radius, close to its ground truth. The stellar-halo flattening q_star(r) has strong constraints on the underlying DM shape.