Admitting he hasn't worked with it before i think was a decent sign. Most won't even tell you that until its too late or until you have learned the hard way.
Still, everybody has to learn somewhere, and if he is familiar with other EMS then I don't see him stuffing things up majorly. The only real reason you would take it there i guess is go "well, look, you're going to be learning off the whole thing, and it may may off more for you in future -- so i want much discounted rates". Paying a tuner to "learn" how to tune a system is asking for trouble.. and unfortunately it happens a lot out there. Reason why i think quite a few people do get ripped by performance workshops.