https://www.youtube.com/watch?v=T2goz1ghXXk&feature=youtu.be
In 2019, 971's design revolved a simple 2-stage elevator with a rotating arm, which could move separately. Their manipulators were also made simpler by combining both hatch and ball into one suction for both. This made their robot incredibly more simple, reducing degrees of freedom.
The rotating arm allowed them to move items from the front to back, avoiding time wasted on 180 turns. Instead of spending time during matches turning, most of the pathing was back and forth in a straight line. You can see in the match video that they almost never turn, giving them a super efficient cycle time.
On the idea of fast cycles, their frame was 19 x 25" and weight was around 92 lbs (including bumpers, battery). You can see their elevator was very lightweight, helping them zoom around the field,
Remember that in a match, cycle time is key, so robots need to transport game pieces to where they need to be as quickly as possible.