Interviews like this are a two-way thing. In this case, I'd pick up the vibe that this was a company cursed with NIH and withdraw my application (unless I was desperate for a job or some other overriding factor, of course).

Technical interviews (much as I hate the whiteboarding bullshit) do give some insight to the interviewee about the kind of work and codebase they'll be dealing with - like the time an interviewer told me "We're really enthusiastic about MongoDB!" - OK, thanks for the coffee, I'll see myself out....