High end databases are often run directly on block storage. The db already manages allocation and caching so a filesystem just adds overhead and wonky semantics.
And therefore your nitpick that a database will consist of files is wrong. (not to mention that the article is not about files as an implementation detail, but as files about a user interface)
What is this magical "high-end" database that operates without the use of any "files"? Certainly not Oracle or Sybase. Sure, they have "data partitions", but the database executables are distributed and stored in files. And what is the magical file-less operating system that they run on? Ooooh we're in "files are extinct land". Where nothing needs files.
