We have the same HWH leveling system on our Jayco Class C. Yes, they work in pairs.
If one jack has made contact, but not the other side, the manual suggests lowering (front or back) until the other, non-contact side makes contact and raises the coach 3/4".
From the manual:
7. After the vehicle is level, the jacks not used for leveling may be extended until they touch the ground. This provides additional stability against wind and activity in the vehicle. Do this by pushing the jack control lever to the rear and/or front as needed to extend any remaining jacks, until they contact the ground and lift the vehicle approximately 3/4 of an inch. Do not use the right or left extend positions.
I've attached the manual. I hope this helps! Good luck!
PS. I'm by no means the world's most proficient person when it comes to leveling the coach.