The power button is still necessary to give a secure, hard "on switch" to your scooter.
Upon turning it on, it's in this idle state, the blinking rear light indicates it's powered on but the scooter isn't turned on. Hitting the on button with the remote turns on the scooter, before this, you cannot use or recognize the scooter, it only keeps it idly powdered, probably way less the idling power of the ninebot app lock.
Turning it off with the remote puts it back in this locked, idle state. If you want to completely cut off power, you must hold and press the button like before the mod. This is still secure because another person cannot use or turn on your scooter without the remote.
Hope this helps clear the confusion.