I'm really not sure on that sorry, I have only my single personal experience to go on, so I can only tell you what happened with mine and what I think based on that but it is not really easy to generalize based on one case.
They are not very informative/transparent about anything so it is very difficult to venture a guess even.
I would think not requiring a visa would make it easier and less likely that they want an interview, but it seems to be a discretionary thing so they could still ask if they wanted.
If your application is past the "average" processing time then you are allowed to email them an application status query, you might want to try this if you haven't already.(Although they pretty much ignored my one that I sent)