Radios can still work without an antenna - the range will just be measured in inches. If you’re like me and use multiple phones (work, personal, testing, etc), and keep at least two in one pocket… A cut antenna won’t do you much good.

A real kill switch should cut power to the radio entirely. Which may be exactly what the software switch is doing. The radio controller may just be too integrated into the SoC to have a hardware kill switch.