Not at all! It's like porting a program which expects there to be a TCP stack to a system which doesn't have one, and wiring up a component which responds to all HTTP requests with 404 instead of letting it hang on an infinite loop or crash. Say it uses a browser for rendering, but in the original you can also fetch websites, and the assumption is deeply baked into the code.

If your choice is between playing whack-a-mole with all parts of the system which might call out, or just issuing a 404 (after all, if there's no Internet, you're not going to find a web page on it), that's a reasonable way to solve the problem.