Would you buy a car if when you took it for a test drive, it had no engine but instead the salesman sat next to you and made "vrrm vrrm" noises for 20 minutes?
Reducing server load makes sense. Use a CDN or proxy, and aggressively cache responses.
Adding an entirely faked backend response, so that the examples don't actually show the real traffic it would generate is both adding complexity to the demo, and potentially giving a misleading picture of how usable the library is: for all we know, it's too slow to use as the examples show, because a real HTTP request to a backend is going to be slower than a javascript function returning a pre-determined string.
The library is displayed fully functionable, but other parts are mocked. Your example is asinine.