With this patch, people can use firmware in SD card if they want; Without this patch, people never able to use firmware in SD card if eMMC firmware exist (even if it's broken).
Most boards I know have the ability to bypass the internal eMMC.
One last thing: I know a number of projects developing devices using our modules that have a SD card slot for data exchange (e.g. config data, log files, data acquisition and export) but that don’t want endusers to boot the device from the SD card (possibly using unauthorized firmware).
For factory use, there’s a signal on the mainboard to disable (until turned back on by software) the on-module eMMC and (if available) SPI to allow booting from the external SD card. For field use, this signal is unaccessible and can not be asserted…
Hope this provides one example to how different use cases can play out...
Thanks, Philipp.