I think this has a bit to do with the song-and-dance ritualization of the hiring process. Employers and employees can both get caught up in saying things they think the other side wants to hear, and when one side presents a question that the other side receives as signalling--you may say "We expect you to work as long as necessary to meet deadlines, even if that's until 10pm or later" and they may hear the stock "Are you a hard worker"--they do what they always have done: signal back the appropriate response.
I think it's appropriate to be very explicit. Call out the issue. Tell them you aren't signalling. Tell them you really mean what you say, and that if they're going to get burned out from that, then your shop isn't the place for them.
I think based on your responses you have the right attitude.