Sounds great, even utopian.

In almost all environments I've ever worked in, telling executives that you can't deploy a new feature because you've exhausted your error budget for the month is not acceptable which renders this system of "failure budgets" moot.

I've also spoken with Googlers about their devops/SRE responsibilities and I've gotten the distinct impression that what is advertised as being the organization's "best practice" is not in fact the common practice.

Measuring and tracking error budgets comes at a large cost, and enforcing failures budgets is rarely a politically effective initiative as an engineering manager.