I think this is a good example of "AI tools are not as good as users think they are". If you're having problems with AI tools not checking to see if a component already exists, then they're not ready for prime-time on your codebase. The solution isn't to stop caring whether or not you're using reusable components, the solution is just to acknowledge (regretfully!) that AI coding is not good enough to meet an appropriate quality standard without more supervision than you've been able to use it with in the past.