That's not the point. Family Boarding requires empty seats so families can sit together. Southwest doesn't appear to limit the number of EBCI sold. It defeats the purpose of family boarding if 2/3 of the plane board before families.
JMO but Southwest should attempt to limit seat saving and try to limit the number of EBCI sold so customers who purchase EBCI board before families.
HISTORY--SWs boarding system motivates passengers to line up and board as soon as they are allowed. Push back is at or even before published time. Assigned seats means some passengers will wait until the last minute to board. Too many passengers line up at T10 the plane is delayed.Southwest started with short intra Texas flights. The quicker turn around allowed Southwest to schedule one, and maybe even, two more flights. Today. Southwest as longer flights. Passengers with assigned seats want to board early in order to grab limited bin space.
edited to add I'm sure Southwest could, in some way, indicate who paid for EBCI on BPs. I don't think that's the issue.