Prob a simple explanation - Your car had an original engine. It blew up. The previous (or one of the previous) owners went to a scrap yard, found an RA there, didn't know any better, bought the engine and put it in.
Voila car runs so he is happy
<< However, the ECU DOES NOT operate them and they DO NOT WORK on road going cars. >>
The second part is true yes. Subaru used the OEM ECU for rallying from 92-96, so it will operate it if needed. 97 onwards they switched to GEMS ECUs and possibly Pectels later.