Agree, Nightbear. I don't really understand the comments about maintenance. If she's 30% grey, the whole point is that she didn't want to grow it out and have a clear colourline - if it grows out 30% grey and continues to grey naturally, that's still a win. When it comes to colour, she has an allergy that limits the products she can use. Showing Jack Martin's pics off Instagram don't mean much, as he's likely using products that contain PPD.
When I still had acres of lockdown roots (around 15% grey at the top of my head) I asked my hairdresser if it was possible to give me grey highlights (note, not even whole head grey) instead of blonde ones so I could start to lean into greying a bit, and I was told to forget it. It's useful to me to see that there are places in London that will have a go at "leaning into grey" colour.
I'd still like to see something similar tried on this side of the pond with PPD-containing colour. If anyone can point me towards more case studies, I'd be chuffed.