Q:

What does it really mean? "Business as usual is not our motto"

See this conversation

Lady: There's gonna be a couple of interviews today, Ben.
We want to make sure that we both find the right fit.
Business as usual is not really our motto, so we hope you have some
  fun here.
This is the first time we're hiring senior interns, so some of our
  intern questions may not exactly fit
your profile, but we're gonna go for it anyway, okay?
Ben: Fire away.
business as usual (idiom) a way of saying that things will continue as
  normal despite a difficult situation

So, does she mean "our business will not continue when there is a difficult situation"?

A:

I don't think the "difficult situation" circumstance applies here. In wikipedia we can find two meanings, and my impression is that it is the second one that applies in this case:

The normal execution of standard functional operations within an organisation, particularly in contrast to a project or program which would introduce change

What that statement suggests is that, rather than stick to old formulas, they are willing to introduce innovation, such as hiring senior interns. (In most companies, interns are junior workers.)

