Not quite. If your native app becomes attractive, Apple might replace you with a built-in clone and then use that as the reason to kick you out of the app store.
If I remember correctly, that's what happened with flux.
The term GP is referencing is Sherlocked[1]. As someone familiar with the iOS jailbreaking ecosystem circa 2010, you could definitely loan the term to apps that are from outside their walled garden.
That said, it would be silly of them not to in some of these most obvious cases: a flux/redshift comparable feature is now built into most OS’s as we’ve become attached to our devices, and Sherlock was argued by critics of the term to be a natural progression of iterating in their file indexing capabilities.
It's not properly built in. OLEDs support full conversion to red-only light, allowing you to preserve your night vision. No other app or built in implementation except f.lux and cf.lumen allow for turning all colors off except red. This is the main reason that I jailbreak my android phone (a oneplus). Not ad blocking, not side loading apps, but because I want to not get my eyes destroyed every night when I try to go to the bathroom and use my phone as an impromptu flashlight...
What the fuck guys? Do you just not care about astronomers? Why is it that no one has properly implemented all of f.luxs features?
On iOS have you tried Settings > Accessibility > Display & Text size > turning on Color Filters and sliding intensity and hue to the far right?
Maybe set the triple click shortcut to Color Filters?
I am not aware of a sherlocked being kicked out of the App Store for duplicating features of Apple’s version, though. That was quite a bold claim, asserted without any example.
If I remember correctly, that's what happened with flux.