A deep understanding of your tool set is a huge advantage.

That is "coding fast". Coding fast doesn't mean literally churning out a lot of code and pull requests.

Managers often have trouble recognizing the difference, though. Even if they know the difference, measuring actual productivity is difficult and subjective, measuring number of pull requests or number of JIRA tickets closed is easy and objective.

> easy and objective.

that’s the worst kind of data - gives a meaningless feeling of objectivity.