How are they "still" files? The never have been files. They are some value that is part of the HTTP header. No one would call the HSTS value a text file, even though it's a string of printable bytes in the HTTP header that is stored somewhere on the hard drive by the browser, just like a cookie.

What is your definition of "file" that precludes calling these text files, files?

The word "file" has a very broad definition. HTTP/0.9 itself could be accurately described as a protocol for sending a text file as a query and receiving one in response. A basic HTTP client can be implemented by reading and writing files into netcat.

The entire HTTP header is a text file.

Where would you digitally sure a JPEG that's not a database? A file system is a database. I guess arguably it's a record if its in a non file-specific database?