I think that must be it. The system prompt is likely it.

Just yesterday was I talking to a customer who was so happy with our "co-pilot" compared to ChatGPT and others that he wants to roll it out to the rest of the company.

We use Azure-OpenAI + RAG + system prompt targeted at architects (AEC). It really seems the system prompt makes all/most of the difference. Because now, users will always get answers targeted towards their profession/industry.