Why would I care? I have <30 ms ping to AWS. Maybe there's an argument for this for something like realtime-ish like games, but this feel likes a massive premature optimization for anything solving typical business problems.
That's not meant to be a snarky question, I genuinely don't understand what business problem that's going to be solved by saving at most 30 ms. Anything written in Rails/Django, talking to a DB, etc. is going to have request latency dominated by other parts of the stack.
We have some benchmarks comparing us to Heroku (on AWS) and the performance gains from faster networking alone are nothing to sneeze at: https://fly.io/blog/turboku/
If the value prop is that you're Heroku, but faster, I can understand that.
I think it's misleading to say that deficiencies of Heroku have anything do to with AWS though. It's really, really easy to set up anycast [https://aws.amazon.com/global-accelerator/] with ECS [especially if you're willing to pay for Fargate]. If your product does something meaningfully different than that, I'd love to know more.
NB: I'm in no way affiliated with AWS or Heroku, just have experience with both in the past.