No offence, but you work in a bubble of sorts. In enterprise we are absolutely expected to run against a wall - preferably fast.
Sure, you have requirements from management. So do architects and engineers for building bridges. Yet they still have a duty to build bridges that don't fall down.
Fortunately, integration-oriented projects have arisen more recently such as https://kernelci.org/ and https://github.com/os-autoinst/openQA/
Anyhow, it would make me a bit sad if the v8 team is writing unit tests tightly coupled to the implementation. I've messed around with the codebase and I didn't see tests like that - could you point to some?
It’s not even necessarily experience because I see the experienced devs do this all the time. But your good developer will know that when the feature is so important that it needs “rushing”, aka straight to prod or, skip QA etc then that’s exactly the time to stand firm and write those unit tests instead of throwing crap over the wall and making it next weeks defect.