The problem is that 3 narrowband wavelengths doesn't add up to very much light. If we call visible range 400-700 nanometers, and bandwidth is 1nm, then you are throwing away 99% of visible light.

I thought 'Nah that'd never work' because I was thinking of the lenses stacked. But you're talking iPhone 11 Pro style. Depending on the properties of the glass that could actually work quite well -- though It may require a standard 4th lens for other optical properties these aren't suited to. White balance for instance, may be hard in this case, I'm not sure.

Up until a few years ago I would have said 'No way. The software isn't there yet, and it'd be prohibitive from a cost/processing power standpoint in mobile form factor.' But... see previous comment on iPhone 11 Pro.