Sure, but in every environment? If a developer is pushing a feature that's mostly business logic, it's probably okay to test in a single-AZ environment. Given their setup, it looks like they still have QA and a final go-no-go test in staging. Issues from a multi-AZ or multi-region setup, should be infrequent enough that you don't need to catch them at the development stage.

I'd wager that they'd have far more issues from sharing a development environment between developers who are all pushing unreleased code to the same environment than they'd have from differences with the production environment. It should be pretty easy for a developer to spin up a simplified environment on demand from a branch or specific commit to do their testing. As a bonus, anyone reviewing code can spin up a similar environment from a pull request to ensure that code does what they think it does.

Infrastructure as code is a good first step. Embracing the freedom you get from that reproduceability is the next step.