Problem TL;DR:

"With staging:

- There could be differences from production

- Multiple people can't test at the same time

- Devs don't test their code."

Solution TL;DR: "Test your code, and push to production."

They completely misunderstood the problem and their solution literally changed nothing other than making devs test their code now. Staging could stay as is and would provide some significant risk mitigation with zero additional effort.

"Whenever we deploy changes, we monitor the situation continuously until we are certain there are no issues."

I'm sure customers would stay on the site, monitoring the situation too. Good luck with that strategy.