Hi Maciej, demo link added in the description.
This is really annoying for beacon contraptions. And I think this should be a pretty easy fix. If this delay existed for performance concerns in early versions, may I point out that many red stone components works fine on 1tick bases. Please just fix it.
I can confirm that in the newest update 1.16.201, foxes do not harvest berries.
Confirm this happened on my realms sever.