There is more than one way to do things. Bottom balancing seems to be a viable option that DeWalt has chosen to patent
. I thought it was interesting, a cell level BMS with shunt loads used to actively bottom balance. JR must be having a love/hate relationship with this
I have to disagree with your last reason for top balancing. If your controller has a user settable minimum input voltage bottom balancing will prevent any cell from being killed. You will kill one or a few cells if they are top balanced and the BMS fails to shut off or turn down the controller. The controller's low voltage input limit won't be able to catch a single cell pulled to zero volts if the rest of them are still a little above the minimum voltage. With a bottom balanced pack no one cell will be pulled under because that is where they will be together. They will all be dropping so the controllers low voltage input limit will kick in to limit amps and protect the pack.
That said, I have a top balanced pack at this time. Having tighter bounds on what is happening when I'm in bed (charging) is more important to me than protecting cells while I'm there in control. My smallest cells (by some slight amount I haven't seen) aren't regularly reaching the highest charging voltages to shut off the charger.