The point about a terminal disclaimer is that this is possible in the U.S. and not possible in Canada.
One of the Canadian inventors who belongs to my organization files his patents in the U.S. because he can make use of this terminal disclaimer opportunity. It allows him to continue to add embodiments to the patent.
It doesn't extend the term. It's an effective way of continuing to do the work on your patent as part of your filing and to advance the embodiments that are included in it as part of a single filing, whereas in Canada you have to have all of those embodiments thought through and completely documented as part of your application. That's just a more onerous process. It's easier to use the terminal disclaimer in the U.S..