Yeah, I realise that it could be really challenging/high maintenance to keep cool-toned. And I suspect that when you do see it done (like the Jack Martin Instragram) it's something that the colourist has really specialised in, so you really have to work to find someone with the right skills. This is all why I am glad to see this article, and I'd like to see more that don't have the PPD restriction. And I would also like to keep an eye on Sali's hair and see what she does with it/how it changes as her roots grow in and she finds the level of maintenance she's comfortable with.
This sort of info is really hard to find. If you look hard into "maintaining grey hair" it's all about 20somethings rocking a cool silver do, not about us slowly-greying types trying to work out when and how to step away from pretending to still have our youthful hair colour.