I might be missing something but it doesn't look like the TWI sensor example in SDK 15 even uses the TWI sensor library. It looks like it uses the driver directly.
Also can you use the sensor library for one device and the driver for a different device concurrently or is this not recommended? I ask because I want to use the lis2dh external driver but add another sensor as well and right now I don't have a good TWI sensor example.