This is getting out of my wheelhouse a bit, but I think it's decrypted real time on the ECU side. Brian @bri3d (won't let me tag him, and he never comes on here) would know for sure. You can't directly read what data is on the ECU, you can only overwrite it.Does the ECU decrypt the data in real time or is it decrypted once the flash finishes? I'm asking because the best way I learn is from someone else's work, then I fiddle from that basic knowledge. So my questions about being able to read the current flash parameters is to get a baseline for what is acceptable and figure out why something was done. This platform sounds super cool and I think I would go this route once I decide to do IS38, MPI, E85, LPFP since I don't want to fork over a ton of cash for something I can feasibly do at home.
So to the question above about having a good baseline tune and then "adding on" the open source flex fuel stuff....nah that won't really work. You'd have to overwrite the entire calibration data.
If you want to start digging into tuning and looking / comparing some example tunes, the discord group is probably a good place to be / to start