The ones offered by Porsche, from the factory, are very small and something their engineers have deemed to be within the acceptable tolerances for the suspension, steering and related components.
Porsche is not conservative about such things, they build their cars to be driven, hard. Launch control on a BMW is limited to, what, 15 times? Total?
On a Porsche, they say “as often as you want.” So when they make a spacer that is only 5mm, that’s what they can accept.
Spacers change the stability, change the stress loads, possibly compromise the wheel-to-hub mating surfaces, add unsprung weight and are not likely crash-tested on your car.
I had them on a car briefly, because I liked the look. After learning more, I opted to remove them. It is possible that, like many who have posted here, you can run them for a long time and not have any problems. Just think about what it is worth to you and consider the type of driving you are doing. Maybe call your insurance company and ask them if there are any issues if these are installed and there is an accident? Just to make sure they wouldn’t disallow your claim.
I am in the “yes, they are dumb” camp, but good luck and happy driving with whatever choice you make! (Sincerely.)