To clarify the issue:
You can't actually "create" a template. Any Space page (or Category page) can be transcluded. It doesn't have to contain any special markup or be designated as a template by its creator.
So, if you have a Space page called My Dog Fido, I can turn it into a template, without your knowledge or say-so, by going to Mary Queen of Scots and typing {{Space:My Dog Fido}}.
Now, anybody looking up Mary Queen of Scots will read about that thing Fido used to do. But that will be entirely my doing, not yours.
Which sounds bad, but only Mary is affected, and only what the reader sees - the stored page is unaffected except for what I typed in. And of course I can mutilate Mary Queen of Scots in much worse ways. It's a wiki.
Under the new rules, {{Space:My Dog Fido}} is now specifically illegal, whereas other vandalism is only illegal in a general way. This of course makes no difference to a vandal, it only impacts legitimate law-abiding users doing legitimate things.
On the other side of the coin, even if a page looks like it's supposed to be a template, it's not a template if it isn't called. It's just a dead page. Its creator can't endow it with any evil powers if nobody calls it.
99.99% of users don't call Space pages as templates (you know if you do, because you have to type {{Space:...}}). So long as you only call official templates, your template calls are at no risk to unofficial activity.
(Strictly, that's only true if images used by templates are also protected. Though there isn't much anybody can do with an image, apart from privatizing it.)
