This sounds really similar to https://www.mobvoi.com/us/pages/ticwatchpro which is a Smartwatch with a dual layer display, one of them is e-ink, the other is an AMOLED display.
Do a search for hybrid eink LCD display; Apple and others were looking into this 10 years ago; the Pixel Qi's 3qi displays were apparently manufactured and used in at least some products, then Apple applied for a more complex patent as well. As far as I can tell, both systems seem to use a layered display.
https://www.pcworld.com/article/165724/bye_bye_kindle_netboo...
https://arstechnica.com/gadgets/2011/04/apple-exploring-hybr...