I don't know much, but this isn't surprising based on the little I know.

Transformers predict the next token.

If your question is at the end of the prompt, the start of an answer is a more likely next token than if the question is at the beginning of the prompt followed by a ton of other relevant, but non-question-forming tokens.

Still, if you had to put the question at the beginning of your prompt, a transformer is more likely to give an answer than an RNN.