Yeah, you are right. The motor min could be set to the same as motor max(but negative). But the limiting factor is not the motor current but the battery current, and thats set as high as it can be to be safe for the battery.
The R2 has a 12Ah battery and going above a battery min current of -12 A means exceeding 1C charge rate, which might degrade or damage your battery. This is of course a sliding scale, if you set it to -15A for example, you’ll probably be okay and you wont use the full brake that often anyways so you might just lose a few % lifetime. Though if you want the same torque no matter the speed, you would have to set the min battery to the same amps as the min motor amps! Then you might overheat your battery or cause internal chemical damage to it. Not advised.
The technical reason behind this is that 500 watt power at low speed would use maybe 10 volts and 50 amps. Multiply amps x volts and you get 500 watts. For higher speeds the motor needs a higher voltage and 500W might use 40 volts and 12,5 amps. 40 times 12,5 is still 500. When the battery supplies power, it will always do this at the current battery voltage, so if you use 500W, the battery will always provide 12,5 amps, regardless of what speed you are going. This is transformed by the Vesc motor controller.
Mechanically, power is torque times rpm. This follows very close to the amps x volts relationship, meaning 500W at low speed gives low RPM and high torque, 500W at high speed gives high RPM and low torque.
The relationship between power and battery current is the same for both throttle and braking, so 500W brakes give high torque(high motor amps) at low speed and low torque(low motor amps) at high speed, while the battery still sees -12,5 amps.
And as you might be thinking, we have already exceeded the motor min of -12A at 500 watts of braking.
This relationship is by the way also present on acceleration, where the very high motor max of 80A can only be sustained to about 1/3 of the top speed, after which the power output tops out at 2000W since the battery cannot supply any more power. Thats the maximum i’ve got at least, with 30A battery max.
Also, if you use the app you’ll be going bonkers over the fact that you do most(all?) of the setting for one vesc and they are then reported back for both.