I have created a completely new policy for KES 11.1 and 11 clients. As I have understood from the documentation, there's no need for predefined exclusions anymore in KES 11.1 and when creating a new policy all the exclusions are empty (as seen on the image). If I push this policy out to clients that are running KES 11.0.1 the predefined exclusions are also removed. Will this have any negative effect on KES 11 clients that have not yet been upgraded to 11.1?

you might wanna export your exclusions and reimport them on the newer policy just to be sure. I think it only updates the policy settings when you update the version of KES, if you only want to release a new policy and you didn't update the policy you will probably have to fill in the blanks from what I experienced.