If you are serious about the job, then you will get the first class before going. Otherwise, you are telling the people that you interview with that their request for the 1st class is not important in your opinion. Sure, it is nitpicky, but they are the ones hiring you. If you do not want to go through the trouble of getting exactly what they request, then you are wasting your time, as well as theirs by showing up for the interview. You are also cheating your fellow pilots, who are waiting on the interview and could show up in your place, just because you feel that you can make up the requirements yourself.