Glad it worked out. As mentioned, DL seems to save at least the last two rows (on narrow bodies), 12 seats, for last minute assignment. Not sure what is done by the computer and what by a human agent, but I do typically see on the app’s standby list that passengers with the same last name are typically assigned adjacent seats in these rows. I don’t think it’s actually based on the last name, but the fact that the bookings are in the same reservation. I think if one of the passengers is elite then they’re more likely to be assigned better seating closer to the front, including preferred and Comfort+ seats if available (and exit row if eligible).

I think the only issue would be if there were a lot of families on the flight who booked BE and they all couldn’t fit in the last 2 rows, but if there were that many people who bought BE then there’s a greater chance of more available adjacent seats in the rest of the cabin.