You're missing something.
The idea is the brushed controller briefly shorts out the motor windings, causing the magnetic field to build. When the switch opens, there's a big voltage spike that gets circulated back to the batteries by the body diodes in the main controller FETs. We don't want to dissipate the energy, we want to direct it back to the batteries. No resistors.
The cool part about this approach is you can control the amount of braking by adjusting the duty cycle on the regen controller. It will also be able to pump juice back into the batteries even at very low speeds without having to switch the configuration of the batteries.
On my Zappy, the regen current, and therefore the amount of braking force, was held constant by the limiter circuit. This made for nice, smooth braking anywhere from full speed all the way down to a crawl.
The circuit in the link is reconfiguring the batteries to a much lower voltage to allow regen. The problem with this approach is the faster you are going, the more current (and force) you get, and it completely quits braking at a reasonably high speed. There's also no current limiting, which might tend to rip the axle out if you hit the brakes at high speed.
"One test is worth a thousand opinions"