Why does “gio info” always return standard::content-type as text/plain, regardless the filename suffix?

Issue

On RHEL-6, the gvfs-info command reported the content-type attribute of a file based on its name suffix, e. g.

$ : > test1.tex
$ echo 'Mary had a little lamb.' > test2.tex
$ gvfs-info test1.tex | fgrep standard::content-type
  standard::content-type: text/x-tex
$ gvfs-info test2.tex | fgrep standard::content-type
  standard::content-type: text/x-tex

The gvfs-info command was replaced by a wrapper script that invokes gio info on RHEL-7 and removed from RHRL-8 but the behavior is not consistent with the previous version.