That's ok but doesn't solve issues you notice only on actual prod traffic. While it can be a nice addition to catch issues earlier with minimal user impact, best practice on large scale systems still requires a staged/progressive prod rollout.

Yep. This is definitely an "as well as"

Unit test, Integration Test, Staging Test, Staging Rollout, Production Test, Canary, Progressive Rollout

Can all be automated can smash through all that quickly with no human intervention.