No, definitely not. Apple recently restricted apps' usage of URL schemes to check whether other apps are even installed on the phone.
It's possible they could be doing something really esoteric with an enterprise app (doesn't need to go through app review) or an MDM profile (can touch some deeper system stuff sometimes), but given that they're currently in the teaser email capture phase, I doubt this will ever crystallize into a real iOS implementation.
I think they're just trying to get some message out, which is fair enough. FWIW, you can always manually set your iPhone to greyscale in system accessibility settings, which they do point out themselves.
It's possible they could be doing something really esoteric with an enterprise app (doesn't need to go through app review) or an MDM profile (can touch some deeper system stuff sometimes), but given that they're currently in the teaser email capture phase, I doubt this will ever crystallize into a real iOS implementation.
I think they're just trying to get some message out, which is fair enough. FWIW, you can always manually set your iPhone to greyscale in system accessibility settings, which they do point out themselves.