My view is, everyone has access to chatgpt and github copilot, and so the idea is to provide value in excess of what chatgpt/copilot can do. Part of that is embedding it in the UI, but (especially for internal tools, which tend to be shorter) the improvement isn't huge over copy/paste or using copilot in vs code.
However, beyond UI integration, we can intelligently pull context on related files, connected DBs/resources, SDKs you're using, and so on. And that's something chatgpt can't do (for now). The quality of response, from what we saw, dramatically improved with the right docs and examples pulled in.
And yes, gpt4 does much better on JS (React specifically) and Python. It's just whatever it's trained on, and there's a ton more JS/Python code out there.