Good morning,
Have had a shot, a bike with the hub was left at my LBS. Had a try and its very good instant change at any speed.. Cant buy the hub they just sell the complete wheel and switch.
I haven't changed my opinion much since
https://www.cyclechat.net/threads/the-end-of-the-front-derailleur.273637/post-6366173
... but they are offering
https://www.classified-cycling.cc/products/road which is the bits needed to build your own wheels for 1,399 Euros, I didn't look hard enough to find a Pound price. :-)
Whilst that is high, remove the cost of a Dura-ace hub (£150ish) and front shifter (£99ish mech/£275ish Di2) it suddenly starts to look viable. Remember that many of the expensive parts are movable between wheels, so if you do have three pairs of wheels you may only need three hubs and one set of internals.
The SA hub is only offered with 28, 32 or 36 holes, they need to offer no more than 16 if they want to sell to "racers"

Years and years and years ago Suntour offered great stuff but never charged enough to develop the next generation, SA don't seem to have ambitions in this direction, happy in their niche
https://www.sturmey-archer.com/products .
At £500 it would look very attractive to anyone considering Di2.
I love Di2 as despite sounding pointless it makes rides, such as the commute, which you don't feel like doing almost pleasant and I can easily see a two speed hub becoming the accepted standard on expensive bike.
Bye
Ian