Put the MDBT42Q in absolute low power mode

Hi,

I have checked into the power consumption of the Espruino and discovered that it consumes around 5 µA at its lowest.
This is not the lowest power consumption mode given by the MDBT42Q datasheet which shows that is can go even below 1 µA in some cases.
On the nrf5 SDK this mode corresponds to the SD_POWER_SYSTEM_OFF which almost turns off the device and only wakes it on GPIO input or reset.
Is there a way to activate this mode using your programming interface ? Or is there a way to maybe add this function in a custom firmware?
What would be the bast starting point to implement this ?

Thanks in advance for your help !
Kind regards,

Thomas