If you have a 6-connector Sumitomo plug nearby your EFI, the OBD Reader should work. It is the same EFI. With the same communication protocol. The Enfield EFi is a quite simple design.
When I asked the seller of the OBD reader you linked to, "Can this scanner tool be made to work with a 2012 Classic 500 with a Keihin ECU?", he responded, "Sorry, only compatible with euro 4 compatible bikes 2017 onwards."
So, although my 2012 is equipped with a 6 pin connector, 3 pins of which are wired, It appears that RE changed something about the communications protocol when they started making the BS4 /Euro4 machines. I don't believe that the Euro4 500 UCEs were ever exported to the USA. Because we were rolling back environmental controls at the time, they were not required to meet our standards. My understanding is that the US only received the equivalent of Euro3 export bikes, with no manifold air temp sensor and other differences in the electronics / wiring.
What is different about the comm. protocol, I don't know, and I haven't tried hooking up a scanner via a 6 to 16 adaptor. There was considerable interest in this back in 2010 to 2014, and the general consensus was that OBD2 scanners and readers, etc did NOT work. Those who tried, failed, so I didn't personally pursue this. Interest has understandably died down since then, folks have accepted the blinky light diagnostics, and the 500 has been basically dropped from the RE line.
One thing that makes the issue confusing when discussed here in the international forum, is that India domestic, Euro and US bikes are all slightly different, with different ECU numbers, although all are variations of the same Keihin box. Most of the experimentation seems to be happening in India, and documented in U-Tube videos, which is great, except they are in Hindi language and the subtitles seem to not work.
Here's what little I have found out about OBDII communications with UCE 500 machines.
My 2012 C5 (Euro3) has a three wire "DOL" connector, with black (ground), red/white (+12V), and gray (data). According to the Haynes schematic for pre Euro4, this gray wire connects to pin 10 of the ECU. Singh5 calls pin 10 the "KLine" pin.
https://youtu.be/ZpPQzrMPK1U?t=101 I haven't found any reports of Euro3 ECUs working with OBD2 scanners.
The schematic for Euro4 C5 machines again shows 3 wires going to the "DOL" connector, but the wire colors are different, we see Black (ground), Orange (+12V), and Purple/ Blue (data). The Haynes schematic for Euro4 machines shows the P/BL data wire as being routed to pin 30 of the ECU rather than pin 10. Although I haven't seen a documented report, there is some evidence to suggest that Euro4 UCE machines can work with some OBD2 readers.
I'm aware that there exists 2 standard protocols that could conceivably be implemented with a single data pin. SAE J1850 VPW, which is used by Ford, and ISO 9141-2: used on Asian, Chrysler, and European cars. ISO 9141-2 would require some non-standard method to wake up the ECU.
https://obdstation.com/obd2-protocols/It seems that RE changed the system again, when the BS6 were released. Now it appears that there are 4 wires, Black (ground), Brown (+12V), Purple (CAN high), Yellow/Red (CAN low). These BS6 bikes definitely seem to
support some OBD2 readers.
https://youtu.be/4Bf_n7YFwgo?t=75https://www.youtube.com/watch?v=9_BrYxrbWngThis $20 Bluetooth scanner seems popular.
https://www.amazon.com/KOBRA-Wireless-OBD-Scanner-Connects/dp/B01C3HAHCS/ref=asc_df_B01C3HAHCS You do seem well versed in this technology, certainly more than myself. I only have my 2012, US export machine to play with. I'm sure that others, besides myself here in the forum would be interested in having the ability to use an OBD2 reader on their older UCE machine, if you can help us figure this puzzle out.