Modern semi-empirical cubic EOSs are usually attached by complex functionalities, such as Huron-Vidal (HV)-type mixing rules. Although this, practice improves the flexibility of the models, it also complicates consideration of an overall picture of phase behavior. As a result, G(E)-based equations are usually adjusted to the experimental data by way of a local fit. The latter approach tends to ignore that different regions of the thermodynamic phase space are closely inter-related. The present study demonstrates that the contribution of (HV)-type mixing rules to predicting high-pressure phase equilibria can be quite modest and that in addition they may generate non-realistic phase diagrams.