It's true that a company would not be able to gain a "feel" for working with a candidate, but those feelings probably help contribute to noise as much allowing interviewers to ask their pet questions.
Surely a company could objectively learn a great deal about a candidate by looking at a week's worth of git commits and evaluating the final product for correctness/maintainability/optimization.
But still, taking TOO much of the humanity out of hiring ignores the fact that ultimately, a person has to work with other people, so you're right that it's not perfect.