Sure it's reasonable in one instance. But what if every company started instituting these trial week scenarios? Then it quickly becomes untenable. There's just no rational basis for an applicant to "feel confident" in anything that isn't in writing. This scenario is designed specifically to give the employer even more power and leverage in a hiring transaction. The only people who would be willing to jump through such hoops are kids fresh out of college or otherwise desperate folks. It certainly isn't going to bias your hiring process towards "rockstars".