This is strictly a curiosity, not a complaint. as my wife is the Spanish speaker and she isn't really interested in reverse interlinear functionality.
The Reina-Valera 1960 on the WebApp has interlinear capability (OT & NT), while it doesn't on my desktop. I would not have expected it in either place, since I bought the RVR60 standalone several years ago (quite pricey back then) and I don't own a Spanish base package. I did purchase the Extended Feature Set recently, so I don't know if that is relevant.