This is NOT by design based on standards for what these icons represent NOR for what hey actually did in previous IOS versions prior to ver 11.
Apple this is Assinine!
Get either he F program and fix this. Apple is supposed to bring simplicity to computing not complexity such as this. Unless Apple explicitly tags the icon with “disconnect” everyone will presume by standards functioning that it’s meant to turn off the Wi-Fi or Bluetooth radios.
E.g. the power button on a Mac or Windows computer under normal power modes by default will Power off or shut down or present a range of options: Shut Down, Sleep maybe even Lock. These of course can be user changed in settings or system preferences but by default again by computing standards will act upon what is expected.