are you obliged to stop on the runway for 30 seconds every time it rains with, let's say, 9 degrees?
We don't.
The problem is: some interpret the second part of the phrasing in a way that I think is improper.
According to them, every time you have icing conditions and you use engine anti icing for takeoff, even in rain with 9°C for example, you have to runup the engine for 30 seconds before releasing the brakes, which I think is exaggerated.
Airbus FCOM 3.4.70 contains a diagram which gives indications about if and when apply the ground ice shedding procedure.
Any additional procedure is a company point of view, not a manufacturer requirement.