Just realised we had previously discussed this on the other forum.
Accucraft locos are made in batches from China. I'm told that Accucraft UK could have a batch of 100 made, originally allowing for a few non-runners in a batch (reliability appears to be improving). So it is likely that the Superior was only available in one batch. Certainly I've seen around 4 available for sale on the Facebook Garden Railway Trading Group in the last year or so.
The Leader was eventually offered at a reduced price to clear out their remaining stock.
I suppose unless you are modelling the Bowaters/SKLR railway or Whipsnade Zoo Railway, maybe it is harder to accept Superior as a generic loco as the more popular Accucraft UK locos (Caradoc, Edrig & Ragleth, etc.)?
I'm trying to work my way through my expanding loco roster to ensure more of them get used more frequently, so my Superior 'Smasher' is getting close for another outing. It will be getting the 'Smasher' name plates mounted & I'll have another look at the tender draw bar & R/C harness to see if I can improve the running characteristics (it derailed on a problematic set of points & descending curve on a friend's layout, which has also caught out a few more locos with pony/trailing trucks).
Chris Cairns