When configuring the NVS in sysconfig, the indexes provided in ti_drivers_config.h do not match with the actual NVS configurations in the NVS config table in ti_drivers_config.c. What seems to be happening is that the NVS_Config table is created by adding the external config list onto the end of the internal one, but the defines that index into the config table don't reflect that structure; instead they match with what sysconfig shows. Either the backend NVS_Config table needs to match what sysconfig shows, or the defines ti_drivers_config.h provides need to match what the table actually has. 

In the example below, if you try to use CONFIG_NVSINTERNAL2, you actually end up using CONFIG_NVSEXTERNAL.