That's true. The hard wired Fn key gets in the way of client side software remaps, too. Not at all unusual in commercial keyboards, though. And as far as Topre boards go, this one's got all the custom caps to make up for it.
The dream will be a wireless version, with every key exposed to the host…
@Bram: Told you the wings are too wide for Esc! That pair's looking mighty friendly, side by side. I've only one Wingnut to play with here, so I can't compare. But I reckon they need a little more space to flap their wings…