Hi @HardWater,
Enter_STANDBY_Mode() sets some flag in backup register before reseting the system to actually enter PWR_EnterSTANDBYMode() in the bootloader mode. So it enter standby mode before the IWDG(Independent watchdog) is turned on. We have taken this path since IWDG is turned on everytime the system boots into the main firmware and so the reset is required to prevent the IWDG being turned ON.
Also PWR_WakeUpPinCmd() is not currently used in bootloader which enables the wakeup pin usage in standby mode.
I am hopeful to sort out all these issues in the next release of the firmware along the lines of Photon release where the IWDG will be enabled only on user request and thus enabling true low power operations without reseting the system when Spark.sleep is called.
Thanks,
Satish