My guess is that nothing will happen if you are GS green and you push the ALT knob with GA ALT higher than your actual altitude passing. But I’m not 100% sure and no FCOM with me now. I would love to try it but I will be only flying on the 22. Vacation time. You can try it by quickly pushing the ALT p/b. If by any chance it starts to climb, quickly vertical zero, arm approach again, VS-1500. You will be on profile in no time.