Hello,
when you decline after you have accepted we notify Shopify and we block the other services as well. Some of them may leave their cookies on your browser but on the next page load, these cookies can no longer be used by these services as these services are blocked. Cookies will be removed automatically from the browser in most cases in two days. This is the optimal way because removing cookies that have already been created and are not used anymore doesn’t make any sense as this behavior is something that browsers are handling now.