On modern high-end devices and the latest Android versions I wouldn't worry about the difference between the KCAL and CF.lumen, performance-wise it should not be noticeable.
As for approval, a lot of things have changed in requirements and rules on the Play Store. If you need odd permissions you need to justify to Google why; specific versions of libraries you have to use; mandatory API targets (the bane of useful apps as every API increase adds more restrictions); my apps have always been on the edge of regulations, because while they're useful, they often use techniques that abusers also use. Difficult line for Google to walk (developers at large have unfortunately proven that they cannot be trusted to have the user's best interest at heart), and they're Google so they also don't really care. I mean, back in the day when Microsoft was still a player, their store also had a review process, but they had very clear rules and regulations, and you could talk to / argue with / convince the reviewers - they weren't below making exceptions if justified. You'll never have that with Google, they smell something, you're out. And this update is particularly on-the-line, so...
Also, CF.lumen requests your location periodically (if you have location auto-update turned on) to update sunrise/sunset time. It does this in the background service its running anyway. And while it doesn't use active location polling (it just asks the device if it determined a location recently, and if so, where are we at? 100km resolution is fine for what we use it for) so no power is used, there are rules against this and doing it can get you banned from the app store. At the same time, the form to justify this behavior in the Play Store developer console doesn't actually work. Classic