And yet we can see Gemini do what I wanted, so it's clearly not impossible.

What you've found is a prompt that returns what you want on Gemeni. That's all.

It's a prompt I've been using for years. Gemini has been the best of the bunch, but Nana Banana, midjourney, etc, all did okay to various degrees.

GPT Image bombed notably worse than the others, not the original picture itself, but the complete lack of recognition of my feedback that it hadn't got it right, it just doubled down on the image it had generated.