I believe facebook has quite complicated A\B testing system with 100+ experiments on run. It’s quite difficult to track all possible combinations that managers willing to test. No QA can check 100! (factorial) combinations.
I worked on similar size project and it’s understandable problem. There is no economical reasons to make perfect experiments.
Thank you for response!
Event without redux/mobx, you can delegate all state management to the top level component, and still benefit from stateless components.
In this case some top level component still should have state or connection with store.