For an advanced history class, where students are expected to be able to make informed opinions about complex issues, this will work (and I suspect most advanced history classes don't focus much on memorization, or even tests for that matter).
But for general education history courses, the notion of "why" is just as much memorization as a list of dates. What if you disagree about the "why" that the teacher/textbook claimed? You'll lose points.
Besides, for all the history courses I've taken (just gen ed ones), tests weren't a big part. There were usually short quizzes on sections of the text book, which were testing for reading comprehension more than memorization. Essays and research papers were most of the grade.
