True, the deformation and stress values are not realistic under plastic deformation.
Yes, "0" for compressive and/or tensile strength means yield strength is used. For ductile materials, the supported failure criteria are von Mises and Maximum Shear Stress, which both use the yield strength. For brittle materials, the yield strength is "0". In that case the non-zero compressive and tensile strengths are used to compute the danger level using the Rankine, Coulomb-Mohr, or Modified Mohr failure criteria.
If you feel so inclined, non-zero values may be entered for all three strengths, allowing use of any of the failure criteria -applicable or not.