I disagree with the author's explanation as to why all questions are algorithmic. I suspect the real reason is due to the US dominance in tech and the popularity of algorithmics in US academia. Indeed the parts of computer science to do with logic, formal methods, semantics, mathematics of program construction etc are, I am told, often described in the US as "Eurotheory". This is a great shame. A new graduate arrives at Google fully trained in algorithms as mandated, but is unlikely to need to implement any of them during their career. It is far more likely that they will need to glue existing systems together, consume APIs, author APIs etc. "Eurotheory" would much better prepare them for this.
As an example, consider that we could be asking questions on API design: get candidates to work through their semantics/axioms (introductory forms to create objects, methods to transform and eliminate them). Get them to write out high-level testable properties such as the way objects compose, associate, commute etc. Using types to enforce invariants etc