Added to my comment, but basically S3 is not a CDN - it doesn't have PoPs/anycast.
They _do_ use anycast and PoPs for the DNS services though. So that's basically how they handle the routing for buckets - but relies entirely on having separate subdomains.
What you're saying is correct for Cloudfront though.
They could do that, but they have absolutely no incentive to do so - all it would do is cost them more. S3 isn't a CDN and isn't designed to work like one.
You have a sole ip address. All traffix routed to nearest PoP. The PoP makes the call on where and how to route the request.
Lookup google front end (GFE) whitepaper. Or thd google cloud global load balancer
That front end server that lives in the PoP can also inspect the http packets for layer 7 load balancing.
https://cloud.google.com/load-balancing/docs/load-balancing-...