Come new Euro-Bollocks time, there's always a grace period where dealers can punt on residual stock. Don't know when this one ends or if it's still running (and the French have a penchant for doing what they like anyway) but there is no Euro 5 UCE.
Yes, I see that you are correct. This article discusses the situation in some depth.
https://www.bennetts.co.uk/bikesocial/news-and-views/news/2020/april/bike-industry-pushing-delay-euro5A lot of exclusions in the fine print, a long list of non-compliant machines for sale, and the moto industry pushing to delay the onset of Euro 5, which it appears was supposed to be at the end of 2020.
I think you are quite right, those 500 UCE machines are Euro 4 / BS 4.
So all is just as was published back on Jan 31, 2020,
"Royal Enfield today announced that it will discontinue the retail sales of Bullet 500, Classic 500 and Thunderbird 500 in India from March 31, 2020. However, Royal Enfield Bullet 500, Royal Enfield Classic 500 and Royal Enfield Thunderbird 500 will continue to be sold across all the international markets. .... service facilities and spare parts for these motorcycles will remain available for the current owners across all the Royal Enfield dealerships in the country." How the decision to withdraw the model from RE's domestic offerings, came to be equated with an inability to bring it into compliance with emissions standards is another story, one, in my view, quite similar to the way the Sportster story evolved. The 500s made a poor showing as a percentage of exports after the 650s were introduced, and sold even worse in India.
The irony is, despite a general belief that the model is dead, UCE 500s seem to be maintaining an EXPORT sales level consistent with what they had before it was announced they would be discontinued in India.
When the Classic 350 with the OHC "J" engine comes onto the market, things may change.