Align Technology interview questions

The process took about a month and ran very smoothly. Every person I had contact with was very friendly and straightfoward. First there was a phone screening, then a phone interview, and then a face to face interview with the manager and head of HR.

1) Screening call with HR. Friendly, yet there was some prying, such as "do you have any offers now?" and "why haven't you received an offer yet during job search?" 2) 30-min screening call with the Hiring Manager. Very professional. 3) 1-hour Skype video interview with senior engineers. Interviewers were professional and courteous. However, around halfway during the interview, I received a Biomechanics question (draw free-body diagram of tooth with equations, etc). Since I had read a previous review on this site, I had been well-prepared for this kind of question. There was no notice before the interview that I would have this kind of surprise pop-quiz nor to have pen and paper ready. While I understand that knowledge of Biomechanics is necessary for the position, it feels like a sucker punch to surprise candidates in this way without warning and make them perform under pressure when they're already nervous. Rejection e-mail happened a week later. I received a template given to those who didn't pass the screening call with the Hiring Manager... It was very nice and positive, but the fact that it didn't really apply to me exacerbated the disappointment I felt in not getting through.