DFU package versioning behavior inconsistent

[erinh]

When attempting a DFU update (containing APP + SD + BL) with the android version of nRF Connect, it appears that connect will update the device's application even when bootloader portion failed version check.  On ios and linux desktop versions, it appears that the device application update will not be attempted by connect when bootloader version check fails.  Which is the correct behavior, and which model should be used for planning DFU distribution?  The android behavior is preferred in this case - are there any downsides to using this model even if some versions of nRF connect don't follow it?

[Vidar Berg]

An APP+SD+BL package contains two init commands since the update is performed in two steps, the first one is for the bl+sd update, and the other one is for the APP update. The difference is that the Android implementation will try to initiate the app update even if the SD+BL command is rejected.  Here's another forum thread related to this: 

https://devzone.nordicsemi.com/f/nordic-q-a/46202/dfu-update-error-fw-version-check-failed-on-ios-when-package-contain-sd-bl-app-and-bootloader-version-is-equal-than-installed/182372#182372 

[erinh]

I just wanted to make sure this wasn't a bug or otherwise unsafe I guess, and this says enough.  Thank you for your help.