We had B1&2 last week with EBCI and still had no issue easily finding 2 seats together (we sat mid plane).
Like a PP said, imagine your boarding # if you DIDN'T purchase it!
Remember that A1-15 is for business select and likely won't have more than a couple of folks up there. That leaves 45 people left in A group, plus 17 ahead of you in B. Even though family boarding between A&B seems daunting, you would be surprised how many people DON'T qualify for it since the kids have to be 4 and under. At my airport they were sticklers about it last week, not allowing extended family to use family boarding (only parents/siblings, not grandma, grandpa, aunts etc.)