No, the templating system and CMS do not have procs declared like the second form. The problem was in ad_proc not handling the proc declaration with leading "::", not in the namespace declaration.
The leading :: tell Tcl that that proc goes into the global namespace. Templating and CMS do not have the leading ::
ad_proc -public template::form { command args } {
So the problem wasn't happening. The leading :: is not required in most cases (there's no occurrence of that form anywhere in the toolkit) but not allowing for it is broken.
That is fixed now.
-Roberto