The board is retired and the corresponding core (https://github.com/arduino/ArduinoCore-primo) has been archived. Considering that no one is going to maintain the low power code for nRF52/Primo its better to get rid of it alltogether (and no longer advertise compatibility to 'nrf52' which - imho rightfully - seems to confuse a lot of people.
Waking from deepSleep() is comparable to an hard reset; the sketch won't restart from the sleep invocation but the wakeuup source can be retrieved with wakeupReason()
