As far as I can tell, these were never installed at the factory but were kits provided for pre-delivery dealer install. I haven't found any Subaru part numbers, but for Toyota:
2012-2016 was pz464-10420-00
2017-2020 was pw501-18000
These are part numbers for the main kit and do not include actual sensors, which are ordered separately according to paint colour.
From what I see, either version could be installed for any year. The early kit is a little more plug and play, with connectors to go between the reverse/rear fog light, and the body harness. The late version requires splicing into the body harness to get power.
Installation manuals for both:
https://www.toyota-tech.eu/aimupload...AIM0024181.pdf
https://www.toyota-tech.eu/aimupload...M003_863_1.pdf
It looks to me like both kits are by Cobra/Vodafone, with the early/late kits being variations of the Cobra Park Master R158 and R294 respectively.