Hello Callum,
IOS 15.5 and above have encrypted battery and screen data. According to JC's manual for the V1SE model, you need to jailbreak the iPhone in JBox (or similar method) to decrypt the screen and battery numbers. Then connect the v1se and read the data (this is the only state of the iphone from which you can send the necessary numbers to their cloud. The instructions were written by a Chinese who probably knew English quite poorly :) I guess). After a while you will receive a new package with numbers directly to your v1se reader. This is the moment to transfer those numbers to iPhone without original screen and proceed with non-genuine TrueTone restore method. That's all. You can also unjailbreak. All changes remain. JBox costs about $100 and in my opinion is too much to have TrueTone. Jailbreaking manually is possible (confirmation needed, haven't tried it for lack of time).
let us know if you succeeded.