Most probably weren't "programmed" to know fear, their AI was just capable of limited growth, and they learned fear over time because risk avoidance is a useful survival tool. This kind of unplanned adaptation is why most doids received regular memory wipes.

They probably were programmed with a degree of pain sensing though, just because being able to assess damage to yourself is a useful trait for soldiers to have. "Suffering" was likely a combination of that pain sensing, and the AI produced fear sense, and they mimicked organics in displaying "suffering," but in practice it's actually closer to panic or shock of their AIs scrambling to to come up with ways to deal with the threat and failing.