I agree with this whole post up to here:

 

I can't agree with this last point, though.  Dynamically typed files were a tremendous liberation from the statically typed files that preceded them, in which you generally had to talk to a local wizard to take a file written by a Fortran program that contained Fortran source code (such as the output of the Ratfor preprocessor) and make it acceptable to the Fortran compiler.  The difficulty was that Ratfor had written a "formatted sequential file", possibly with carriage control in column 1, whereas the compiler expected a "stream file" or "editable file", which was something completely different.

(My personal experience with this was on Tandem's Guardian OS when I was porting the Software Tools utilities.  Fortunately there was a library that could read editable files, so the I wrote the Software Tools primitives to accept either editable or formatted sequential files on input and always write formatted sequential files.  I forget how we transformed sequential files back to editable: it must have been either a native utility or more likely the native editor itself.) 

The last widely used statically typed file system I know of was on pre-OSX Macs, where each file bore a 32-bit type (usually interpreted as 4 ASCII characters) that specified the application (singular, normally) that knew how to deal with it.  That was eventually a failure too.