I've also had interviews where they had me do some simple things in cad in the interview but the company had all these custom add ins to the interface so everything was all moved to new locations. To me it looked like a completely different program and I felt like an idiot for how long it took me to do something. I explained it to the interviewer why I was so slow, but I'm not sure they bought it. Similar things can happen though. If you modify your cui at your job and then go on an interview and the cui is stock or worse yet the interviewing company has a custom cui, there is no way you can be expected to be as fast as you are. Just simple things like changing C to be copy instead of circle and it's the way you are not used to would fluster a lot of people in an interview. I mean just take away my custom quick access toolbar and I'd be noticeably slower in some aspects.