There's a layer between your input and the model called an agent harness. It's the bit that guides the model how to traverse the file system, where to search, how the codebase is architected, how to navigate the monorepo.
When you say "Add a default $5 tip to the dialog screen titled 'Tip this waiter?'", what the harness does is supply information on where the strings are, the dialogs, and where the design style containing the PrimaryButton might be.
Cursor is excellent at this and probably pioneered the whole approach. Copilot hasn't really bothered to be more than a wrapper.
The models are the same. The agent implementation is different. I can confirm Claude Code performs much better than GH Copilot with the same Claude models.
GitHub copilot agent mode is quite bad, and advanced premium models like opus4.6/codex 5.3 are making it barely usable.
Claude code and codex are night and day comparatively.
Additionally, GitHub copilot admins can enable/disable models. Each model has different ToS, so perhaps their admin has not turned it on.
I would suggest you not immediately insult people with ad hominem attacks.