To put what Jon said in simple terms, at least, as it was when I was there
We build them at the same time. When you're making one part, make two, when you're making two, make four. It is a lot more work, but as Jon said, it gives students more experience in helping build the robot, often times, the engineer will build something with the student for one robot and give the work for the twin to the student, and simply help if it's asked. The second robot can be good for taking apart and explain things as well as driving. The second robot for RAGE is often mostly disassembled a day or two before a regional since that's our spare parts. It's a great way to learn things about the robot and get some driving practice in. The "evil twin" for RAGE is often beaten on and driven into the ground, as well as making us able to do demos during the competition season on the current game with our "current" robot, so if some one comes to the demo and then comes to the UTC regional (since it's closest to us) it's easier for them to recognize us (as if the bright red shirts don't do it)
Oh, and if you ever want to use the practice facility, contact Jon, who will contact our team leader to get you in. It's on main street in East Hartford and has a soda machine.
