I think the key difference is ESR mentions file attributes at the OS level. You're right that Linux has file attributes, but since Unix/Linux recognizes the contents of a file to determine how to handle said file rather than some arbitrary attribute associated with the file, it isn't limited to certain programs in order to be interpreted correctly. An ASCII text file will generally look the same whether you use vi, pico, nano, etc and regardless of the platform (as long as the shell is the same.) For example, writing a text file on SUN OS and opening it on Redhat will look identical.
On the other hand, a '.doc' file won't look the same if it is opened in notepad or wordpad and many programs won't even open it (Excel, Powerpoint, etc.) These restrictions don't exist on Linux. Hell you can 'cat' an executable file in Unix if you want (it will be nothing but gibberish, but you still have the option)
The wording could be better, but I think that is the general difference (or I may be way off, but that was my interpretation at least)