The report and the previous one for 1.0 definitely contain much more information than the GPT-4 whitepaper. And Google regularly publishes technical details on other models, like Lumiere, things that OpenAI stopped doing after their InstructGPT paper.
Maybe because GPT3.5 is closer to what Gemini 1.0 was... GPT4 and Gemini 1.5 are similarly sparse in their "how we did it and what we used" when it comes to papers
