I would counter with the idea that seniority and programming ability are inversely proportional via The Gervais Principal (mentioned on hn again just recently)
Doing that at a startup would be easy, since you control the whole stack and can tune it to the use case, and almost certainly don't have problems of scale. It's 90% getting the technical stuff in place, assuming you have the budget.
Doing it at a place like Google is a different matter. The job isn't tuning a stack. It's coordinating multiple teams that own different services, and trying to make general-purpose services and frameworks work especially well for a specific case, even in the face of competing demands and standardization forces. It would be 90% political, and the task-specific differentiation required may simply be insurmountable - the extra wrinkles for your use case might cost more in complexity and reliability than it's worth.
What makes you think a Principal engineer is tasked with that? Principal engineers do mostly stuff like create new infrastructure technology like spanner, or machine learning frameworks, or similar stuff. Google doesn't have that many principal engineers, they correspond to director on the manager ladder, but there are way fewer principal engineers than directors as it is much harder to climb the contributor ladder than the manager ladder. Most Google products doesn't have a single principal engineer on the team.
Drive almost certainly has an L8 on the team somewhere. It is a big product. And it could be the case that "find a completely new indexing structure that makes drive search and folder navigation 10x faster" is a L8 task. Drive is indeed a lot slower than I'd personally like and a lot of that comes down to the way that indexing works when you cannot group users together, which is at the very core of the product.
In the terms of that article, Principal Engineers would perhaps be classified as 'losers'.
> The Gervais principle differs from the Peter Principle, which it superficially resembles. The Peter Principle states that all people are promoted to the level of their incompetence. It is based on the assumption that future promotions are based on past performance. The Peter Principle is wrong for the simple reason that executives aren’t that stupid, and because there isn’t that much room in an upward-narrowing pyramid. They know what it takes for a promotion candidate to perform at the to level. So if they are promoting people beyond their competence anyway, under conditions of opportunity scarcity, there must be a good reason.
> Scott Adams, seeing a different flaw in the Peter Principle, proposed the Dilbert Principle: that companies tend to systematically promote their least-competent employees to middle management to limit the damage they can do. This again is untrue. The Gervais principle predicts the exact opposite: that the most competent ones will be promoted to middle management. Michael Scott was a star salesman before he become a Clueless middle manager. The least competent employees (but not all of them — only certain enlightened incompetents) will be promoted not to middle management, but fast-tracked through to senior management. To the Sociopath level.
To be clear: I mean to imply no opinion on whether 'The Gervais Principle' is true nor applicable. I'm just saying that 'The Gervais Principle' is perfectly compatible with Principal Engineers at Google knowing their stuff.