That metric strongly discourages asking questions - which is a critical part of a Senior Engineer's job. When someone is at the level of SE, they have proven t

That metric strongly discourages asking questions - which is a critical part of a Senior Engineer's job. When someone is at the level of SE, they have proven they have skills beyond slinging well-formed code - that's entry stakes for second-tier. They demonstrate a wider understanding of how their work fits into the overall product development, an understanding of customer perspective, and many other attributes. Most if not all of these derive from knowing the right questions to ask, the right people to ask them of, and the right time to do so. The biggest differentiator is that the Senior developer should know when she needs to ask questions to proceed.