And what's wrong with being asked if you had the foresight to do some practice for your sim assessment? And what's wrong with telling the assessor that you did indeed have some tuition and practice because you want the job so much?
You wouldn't take ANY flight test for licence issue without tuition/ practice first, so what makes a sim assessment on a new type any different? I always recommend low hours pilots pay for an hour or two in a similar sim before an assessment - the check ride is not the time to be trying to get to grips with the pitch power couple of a 737 for the first time.
If you do a reasonable job in your assessment and the instructor asks if you have done it before, tell the truth! Tell them how much the job means to you so you wanted to be fully prepared. This tells the instructor that you;
1. Care enough to really want the job.
2. Plan ahead and prepare thoroughly.
3. Display the right attitude towards what will undoubtedly be a steep learning curve should you get the job.
4. Make sensible decisions when faced with challenges.
5. Have a professional attitude.
Whatever you do, don't lie and say you haven't ever been in a sim like it before! I know someone who recently did a good job in the sim (his opinion) and was asked a couple of times if he had practiced, to which he replied that he had not (when he had). He thinks the instructor may have seen through him and potentially his dishonesty is what cost him the sim ride (the feedback on his selection was that he failed the sim).
Just my thoughts on the subject.
PP
ps I did 2 hrs in a 737 sim before my first airline assessment and I KNOW that if I hadn't my performance would not have been good enough to get the job offer (I was all over the place in those 2 hours!!)