There is also a penalty to initiative rolls, -4. And...
From RMSS Core rules page #76:
"If a character is surprised, a GM may limit his activity for his first round of reaction. We suggest a GM allow a surprised character to take only one deliberate action. The actual % activity allowed should range from 0-100% based upon an orientation roll (see Section 21.4)."
A bad orientation roll could leave one without the percentage of activity to draw a weapon, find cover, or attack, or parry with much effectiveness.
So, melee characters cannot "still parry as much as they want without penalty".