jonanen I was playing with emulators (dolphin, melonDS) and heard about how JIT increases performance by a significant amount.
Compared to an interpreter loop, yes. Compared to in-advance whole-program translation, probably not. GrapheneOS compiles every app after each update, so there is no need to JIT an app when it is run. In theory there are cases where JIT can result in better performance than AOT, but those are not the common case.
A bicycle is faster than walking, but a car is faster than a bicycle. Replacing a car with a bicycle is unlikely to improve performance, except sometimes in a traffic jam.