My argument here (<
https://news.ycombinator.com/item?id=37869476>) is that
across all OSes, and for the Web generally, being mindful of monochrome, low-refresh-rate displays is something that should be front-of-mind for UI/UX teams and design.
Many of these issues already exist, e.g., for documents which are likely to be printed on monochrome devices. Colour is useful where available, but it is not universally available.
(And that's before addressing issues such as colourblindness or other disability / accessibility considerations.)
My original comment was not at all specific to Apple (you'd introduced them to the discussion), other vendors, or any specific OS or application. Simply that monochrome and e-ink are increasingly concerns.
But since you raised the topic of Apple, and since, contrary to your initial statement that, broadly speaking, monochrome was "a display technology they never used", I'm both correcting the record, and noting that should there be a monochrome or e-ink prospect on Apple's roadmap, and further noting that Apple rather famously does not announce such roadmaps in advance, that flat/white would in fact fit with e-ink remarkably well.
What that has to say about whether or not Apple is contemplating any such move I am, of course, entirely ignorant.