Yes, it shows them all and always if "Show all file name extensions" is selected, then the extensions obviously are always shown.
On the contrary, if "Show all file name extensions" is disabled, user may manually override it on a per-file basis by unticking the "hide extension" checkbox in file info window.
(And I believe it depends on the app if it decides to create files with this checkbox enabled or not. Well, some apps do not even care about extensions at all, but that's a different story.)