I'be been following this venture since the pre-publicity (it IS on my doorstep!), and had a while to think about the concept, I think the general message here is that calling it a "Gravel" route is optimistic, except in good weather/conditions. The word "bandwagon" is lurking in the wings.
It's certainly not an easy route for the less physically able, or if you don't have the right bike.
Still, it will be interesting for many, as this thread demonstrates.
HOWEVER, speaking selfishly, I'd rather have a route that is much more rideable, even if that means a fair few miles of quiet lanes and back-roads. That would be more accesible/inclusive. But maybe I'm in the minority, maybe most are desperate to avoid cars at all costs?