Kodi’s wiki tends to be a simplified guide for a general user base, not an exhaustive guide. The average users eyes would glaze over if you tried outlining the finer points of refresh rate and resolution switching. People looking for more details on specific topics usually find them on Kodi’s forum, github, or from hardware or distro specific forums like this one.
Setting the UI to 2160p has an impact on responsiveness of the UI. Less so with newer SBC media players than it once did, but I assume this is still why the default resolution is what it is. As for the whitelist that can have a lot of things for people to consider with that one. Not running a whitelist leads to the least amount of potential issues and confusions for a general user base so it not being enabled by default makes sense for that reason alone. The setting is not hidden and nobody is ever discouraged from using it without a specific reason why. You can learn more about the ins and outs of this feature in the following howto…