As a disclaimer, this falls under the "Back then" section of the talk which is an overview of how things used to work. We no longer do things this way.

Publishing a page is running content from a CMS through a templating system. However, the time spent executing templates isn't the only factor in the duration of the "publish". The slides refer to a compilation step (which actually also included a preprocessor step), and includes delegating to a service to copy the resulting page to disk and ensure the write succeeds for all data centers. For data consistency and system monitoring, we essentially treat that entire process as an atomic action and wait for all parts to finish. Additionally, since "publishing" is a core process for us, we avoid doing massive publishes that might risk the systems involved in the successful publishing of current articles. So increasing the number of these for the sake of pushing code is considered too risky. Yes, there are ways of mitigating that risk, but dealing with this legacy problem once and for all is a better path forward than scaling up this solution.