In terms of LLM code generation as well, the well structured nature of a Rails application, where there is a place for everything, a structure for tests to be added, really helps from the perspective of getting a comprehensible application out of it that is easy to modify. In addition to the existence of well tested component for most normal web application tasks, maybe it helps that a lot of Rails has already been based on old-fashioned code generation for 20 years.
I have this same suspicion. I dusted off a hobby Rails app from two years ago I was making with Cursor. I decided to try completely changing the main functionality of the app with the much better LLMs of today and was shocked how well it did with one-shot.
Now compare that to my recent experience with having Cursor help me work on a preexisting Node/React app...geez. What a pain. (It doesn't help that I wasn't the one that originally created the React app though.)
