What's the difference between DFU and iTunes restore in iPhone? The articles I've read regarding this aren't very clarifying.

Does an iTunes restore restore the firmware?  At the end of the iTunes restore (not DFU), I can see "restoring iPhone firmware", but I had a chat with Apple through GSX and the technician told me that this is just "a misnomer", the firmware is only restored in DFU mode.
DFU writes the firmware and then the OS. 
Restore writes the OS only. 


My guess is the misnomer is firmware like carrier updates and modem scripts will be layered on after either OS restore. Also, these names originated when the iOS devices were far simpler. Secure enclave, secure boot chain, forward secrecy and encryption at rest make the update procedure far more uniform. Maybe that's also what GSX is alluding to - you don't really write all the firmware anymore on current / modern iOS devices.