The defense I've seen is that it works reasonably well as a measure of productivity _if_ you're working in a similar team and in a stable codebase.
From what I understand a lot of product teams at FB have nearly frictionless development tooling for their use cases so the pressure is to produce volume.
I call bullshit. Even if you have high-powered tools you still have to spend time thinking about how to use them, and you still continually improve them to reduce line count.
From what I understand a lot of product teams at FB have nearly frictionless development tooling for their use cases so the pressure is to produce volume.