Does that seem unreasonable? I don't have any experience with such things, but it seems reasonable to me. The company decided you'd be most effective in position Y, so they put you there and gave you a pay/benefits raise, and now you're saying "I'd really like to do position X which is less optimal for the company even though you want me at Y and might/probably have already found someone to do X, and my reasons are A, B, and C".
A letter sounds like the perfect medium to communicate something like that.
Yes, it was the right way to handle it, but my impression when I went through it was that it was completely novel to the HR organization and they were reluctant to agree to demote anyone at all, whether they were requesting it or not.
A letter sounds like the perfect medium to communicate something like that.