I'm currently running nrfjprog version on OSX. Version info below:
nrfjprog --version nrfjprog version: 10.9.0 JLinkARM.dll version: 6.70b
When running a nrfjprog -e I expect that the device doesn't do anything afterwards. When monitoring the serial output I still see that the code that was last run is still running despite running nrfjprog -e. I'm using a nRF9160DK to program an external nRF9160 Feather board.