Your comment ignores the next section in the article, detailing how they are caching templates with a high level of granularity, and actively removing template logic that impedes efficient cacheing.
The article goes on to state that delivery times for cached segments of HTML are under 50ms in most cases. While I agree that it would be possible for them to improve the user's perception of the app performance even further via JSON or client-side updates, with the level of performance they described that type of improvement is unnecessary and introduces additional vectors for bugs to creep into production code.
The article goes on to state that delivery times for cached segments of HTML are under 50ms in most cases. While I agree that it would be possible for them to improve the user's perception of the app performance even further via JSON or client-side updates, with the level of performance they described that type of improvement is unnecessary and introduces additional vectors for bugs to creep into production code.