There's some difference in behaviour here between the Circuit Playground Bluefruit and Circuit Playground Express. If you turn on some pixels and then hit Cntrl-D in REPL on a CPX then pixels turn off. On a CPB it they remain on.

Perhaps there are also other peripherals that are not re-initialised too?

Press any key to enter the REPL. Use CTRL-D to reload.
Adafruit CircuitPython 5.0.0-beta.0 on 2019-11-19; Adafruit Circuit Playground Bluefruit with nRF52840
>>>
>>> from adafruit_circuitplayground.bluefruit import cpb
>>> cpb.pixels[5] = (50, 0, 0)
>>> cpb.pixels[6] = (0, 50, 0)
>>> cpb.pixels[7] = (0, 0, 50)
>>>
soft reboot

This is on 5.0.0-beta.0 with the latest library copied in from https://github.com/adafruit/Adafruit_CircuitPython_CircuitPlayground - I am running 4.1.0 on the CPX, btw.