Understanding pattern drafting details, Why evaluate a sewing pattern - V1645

Let's talk details.  Why would you spend time testing the drape of a pattern before cutting?  I'm discussing the particulars of Vogue 1645 in this video. 

Vogue 1645 is a fun pattern.  I've seen many folks sew this one.  I'm reviewing the makeup of the actual design details before deciding whether to sew it for myself.