It depends the charger. If the only other way is through the 2nd port then you are right although imo people with high charge/discharge rates have enough time to do that with one port. But if the charger does support high rate discharging through a resistor bank on the same port then a regenerating discharging is not needed.
eortizr is not clear about his charger

When you are running 2 or 3 classes, having to marshall 2 or 3 races and wrench on cars, even cycling at 45a I find myself strapped for time especially if the turnout is low and each round is coming up quick without any lengthy breaks. I'd never make it on one port.

I went from two complete iCharger setups with their own power supply and Donathen RC resistor banks to the 4S off-road RC Discharger (retails for $399). I race on-road but the 6S 9500mah LiPo that comes with the off-road 4S RC Discharger is more than enough for me to cycle two 4200mah to 9600mah 2S race packs on both channels at 30 to 45A. The on-road version is more money and I suppose comes with an even larger LiPo for the regenerative pack but I'm guessing that's for folks bridging both channels and cycling at the full 70a capacity of the common dual iChargers like the 406/408 or 456/458 that's most commonly found in the pits. Or folks cycling dual 3S or 4S packs.

From my experience with the RC Discharger you can cycle the batteries to a lower voltage per cell while generating less heat in the battery than with the resistor bank. Heat lowers the IR but too much heat will ruin the cells. In order to get a fuller cycle of the complete battery's capacity you would need to discharge the cells to a much lower voltage per cell. But in order to do this without generating too much heat you'd need to cycle at a much lower amperage prolonging the cycling process time. The performance from the packs just won't be the same as when you are hitting them harder at a higher amperage. This is where the RC Discharger shines and offers better performance out of your race packs. You can cycle at much higher amps, to a lower voltage per cell without frying the packs like you would with a resistor bank. Cycles also are greater % of total capacity. For example, 6500mah pack on the resistor bank you may only get 5400mah in the 45a cycle whilst getting the pack up to lets say 115* F at like 3.60v/cell. But on the RC Discharger I can cycle that same pack at 45a to 3.50v/cell, getting 5800mah in the cycle and pack gets to same 115* F or less and see a lower IR (1.0 milli-ohms versus 1.2 milli-ohms).

I switched from a 406 with a resistor bank, and using a x6 to charge, to RC Discharger as well with 2 S6's! So much easier to regen discharge, the overall package is a slight smaller than what I was carrying. So far, I have been very please with the results. I have been 30a charge/discharge.

I’m getting a bit tired of lugging my resistor discharger around. If that thing works in storage mode then damn, makes it a lot better then going into discharge mode, guess when it’s done, then storage mode.
I made a double fan heatsink so it’s safer, but still rather bulky. $50 is not a bad price at all