Indeed – I know exactly where that is, and it would presumably be very easy to make the route go that way – can't be more than half a mile diversion (what happens if we ignore the signs and do that bit anyway?) Not that I've ever biked it, but I've orienteered through there (is pretty hard work doing fine nav through all those earthworks).
Kind of sorry about it being signed – part of the appeal has always been that you do have to navigate yourself, though I suppose with widespread GPS use now that's no longer actually a challenge. I remember on my first ever HONC catching up the Barry Clarke lead group who'd gone the wrong way when I'd navved my group the right way. OTOH in a way I'm glad this year as I don't have much prep time, so won't have to worry so much about the maps.
I have a CX bike, but will be on the full-sus – a decision made ages ago since my 6 month old wrist injury still sometimes hurts on the road bike. Not only that I don't fancy rough stuff on rigid forks, but I don't get the same discomfort on flat bars. Mind you I do have full remote lockout for the road bits and fast tyres (RRs) – do plenty of tarmac in the races I do, and it's certainly not slow on that, so I don't think it will be a problem. It's also probably just as light if not lighter than the CX bike (and indeed most people's CX bikes and hardtails). In the same way I'd enjoy passing people on MTBs on the downhill bits if on the crosser, I plan to overtake lots of crossers on the road sections 😉