I'm late to this conversation about rehabbing vintage D&B AWL, but I've dunked perhaps 25 vintage AWL bags and generally, they come out fine. I use the same process that I use to dunk
Coach bags, and there's an active Coach Rehab thread here, which you may also be aware of. Of the 25 D&B bags, 3 had issues with thin binding leather cracking - they were tote style vintage bags, both in leather and fabric.
I was happy to be able to clean and reshape the bags, keeping them stuffed with towels as they dry. And in fact this weekend, have 2 equestrians drying as we speak. Chiming in late, for what it's worth.