What's up with this page?
According to the extension documentation, there is no fix for the inclusion tags, yet, unless I read that wrong. I put it in the Help namespace because that's where I'm used to putting documents like boilerplates, the contents of which are copied, rather than transcluded. I think putting them there helps differentiate it from regular templates, where changes are easily reverted across the entire wiki with just one edit. But, if a preload page or a boilerplate gets edited, all the pages using that preload or boilerplate need to be edited by hand to reflect the changes. However, I didn't actually try to verify a precedence, I just put it where I thought it would be logical. If WE would rather have it in the Template namespace, it's no problem to move. ;)
Using Help:PageName seems logical to me. Using a template does not work either --anymore? -- as per your link. I must be getting old. Sorry to send you on a wild goose chase.