When I built my electrical system for my trailer I knew that many of the components had fancy features with Bluetooth and app control. My main design criteria was that the use of those fancy features should only be a convenience when used, not a necessity. I develop software for a living. Things go wrong. Vendors drop support. Software stops working. Your phone battery is dead. Whatever. I did not want to risk my system going down or running into a safety issue just because some phone app is out-of-date.
So, in short, yes, you should still add physical controls.
And in this case you may need a physical switch because the BMS went bad or it's having some other issue. I wouldn't want to be playing with wires with the knowledge that the only thing keeping me from getting badly shocked is that some software told the BMS to stop discharging. I would not want to trust that.