I am in agreement with this, and am thrilled with worldbuilding accepting this stance. It also makes the site mesh better with other sites. Regarding:
Caveat: Members are certainly welcome to suggest via comment that a post may get better answers on one of the other sites in the network. There is nothing wrong with the suggestion and its always possible someone didn't know. That said, being on-topic on another site does not make a question off-topic for Worldbuilding.
For a small site such as engineering.stackexchange.com, about one-fourth of the questions on the site come from someone attempting to design a device for a story using real-world engineering principles. These questions have been ruled off-topic for various reasons, even when they have really interesting applications. Unfortunately, before worldbuilding we had no place to send those users. This made for a terrible user interaction for new visitors.
The typical route I take when seeing a good"what-if...?" question on engineering these days has been to route directly to worldbuilding. Since there is no practical application, or testing, and the initial conditions are wild, this site lends itself well to resolve real-world designs without getting into excessively complex models. Overall it is more interesting when we can use unobtanium as a potential material of construction, something which is never allowed in engineering - but perfectly reasonable in worldbuilding.
Worldbuilding solving real-world problems helps the science sites stay a reasonable resource for minds seeking real solutions to real problems. Simultaneously, this allows users access to engineering, astrophysics, physics, and other scientific models to solve unique, fun puzzles and inquiries.