It's a bit faster than the standard ad_parse_ad_conn_file proc, because it doesn't first set a local then check the resulting mime type and preamble.
It probably should, though ... currently the mime type is always returned as text/html. I'm assuming the notion is that the templating system could eventually return other mime types using a different template rendering engine, that kind of thing.
This should become the "standard" way to do this kind of template dispatching I think, certainly the current method used in the CMS and ETP don't work, as you've proven.
