It'll depend on what you're building, but there's some value in rendering React on our backend. For example, we render documents (HTML => PDF) and emails with the same React components we use for our frontend to keep styling consistent. There are also some utils we use (in similar contexts) on both sides largely for things like string formatting or annoying math. Not a ton of stuff, but it's nice to have one bulletproof util to format phone numbers in every context. Another one is payment fee calculation[0], so we can guarantee the user sees the same number they'll be charged.

I think the more powerful benefits are definitely hiring and having a team that can work on both sides (and in that regard I think your points are perfectly reasonable), but there are definitely some more direct benefits in our case.

[0]https://support.stripe.com/questions/passing-the-stripe-fee-...