We did this often enough that we built a chrome extension that lets us reorder diffs in the Github PR UI rather than needing to type out the suggested order in the description.
Anecdotally, we've noticed that using this tool to reordering diffs makes it much easier for reviewers to review PRs, especially when they are large/complicated, which is sometimes unavoidable.
Narratives (what we're calling the extension) is open source and stores no data on remotely, so it should be safe to use on private repos. If your team writes/reviews lots of code - maybe give this a try. We would love to get your feedback, and PRs are welcome
Chrome Web Store: https://chromewebstore.google.com/detail/narratives/ffcilgbo... Source: https://github.com/Naqu6/narratives-extension