i don't think it is necessary or sufficient for all individuals to have a deep understanding of the runtime environment. i agree that if the team needs to ship production code, it would be a good idea if at least one person in the team has a good understanding of how the code runs.

but there are other failure modes -- if everyone on the team is great at writing efficient production code, but no one understands the business context or the problem domain or understands if the problem they're attempting to solve is even vaguely feasible from some kind of theoretical perspective (maybe someone with a decent statistics background could demonstrate the entire premise of the project is flawed, and needs to be rethought, using a blackboard and no computers at all), maybe they'll spend months or years building and deploying a lot of fast, beautiful, completely worthless machinery.