I dont know much about PCSX2s source code but it seems to me like it doesnt really overclock the EE either, the speedhack just changes the number of cycles the emulator waits (between execution?). You could probably do the same with jpcsp but i dont think it would solve your problem. Anyway your right, only a dev can clarify this.
EDIT: after thinking about it, serios answer should be correct, this would only effect performance if the game already runs at full speed
EDIT: after thinking about it, serios answer should be correct, this would only effect performance if the game already runs at full speed