Using a Pixel 2 XL, and it seems to be charging and using way more battery when I flew with my iPhone.

Go back to your iPhone. Charging Android devices from any power source connected via a USB socket is part of the Android operating system.
This is a common complaint on these forums but sadly beyond the control of DJI

Hi Rocky43, my sincere apologies for all the inconvenience that it caused. It was related to the android system and hardware. The Android phone or Tablet needs on-going 500ma to maintain the USB connection, so there is no option for the Android device to disable the charging mode. You can use IOS device as an alternative way to stop the charging. Appreciate your understanding and support.