Your example is for an attraction that Disney *actually doubled the capacity* of. They recognized Dumbo was a problem, and they didn't just slap a $30 "bypass the standby line" upcharge for it. I suspect current Disney considers that a mistake. If there was still a single spinner, there would be more demand, less labor and maintenance costs, and more people would actively choose a LL for it (adding to the value of LL), because it would have longer regular waits. But it was an improvement that benefited all guests.
However, in this new arrangement I ride Dumbo a lot less. I used to ride Dumbo, and planned for it, and now I don't. In the old location, there was a benefit flying over central Fantasyland, that even as an adult I could appreciate, especially at night, that doesn't exist in the new spot, between the building and the trees. Which is better? I would still take the capacity improvements, but hoped Imagineers gave more thought to the site lines while in flight.