The AWS support is explicitly acknowledging it's an issue, while giving a rational reason why it probably won't be fixed (even if you disagree with the reason). The back-compat concern is unfortunate but a good argument can be made it's not in users' interests either (beyond being just a cost to AWS to implement the change).
They're not going to change it just for the sake of some minor path issues that have a workaround. (Side note: They tend to uses headers rather than paths for API declarations). I have personally been bit by this same issue, but I would never recommend they change pieces of the service to accommodate it. It's handled easily in client code. What they could do is make an obvious "gotchas" section of documentation
AWS has done a tremendous job of getting things right-enough the first time. They have never killed an AWS service. They'd need a much bigger reason to version an API.
This is the opposite of that.
In earlier times, we would have both the ability and the balls to treat that unwillingness to uphold the rules we all set out with as damage to the Internet, and route around it. But sadly, AWS has become too big to fail, so the engineers introduce special cases into their products and deploy them.