Yes, it will every time. I expect that's due to the correlations that are built into HYSYS. I've had better luck using Pipaphase or PRO-II to match lab data or actual field tests for GOR. I usually use Pipephase for this type of upstream work because that is it's forté.
The rule of thumb we use around here is that HYSYS is better for gas plant work, PRO-II for refinery, and Pipephase for upstream work. If you have gases with steam in them e.g. TEOR oilfield casing gas then HYSYS tends to work the best but they all have a tough time with gas mixtures containing steam. But I digress. Thanks!
Pete