I don't know if this is the "bw" way but I did a lot of accidental parenting in the beginning before my dd's reflux was diagnosed. I would let her have ALL her naps in her swing. Once we were diagnosed I worked on getting her two main naps to be in the crib. I did leave the catnap in the swing as I knew we would be dropping it soon. That doesn't really answer your question but... maybe he's ready to drop the catnap altogether? When this happened for us it was a slow transition. Somedays she needed it, somedays not. As you probably know, the 45 minute mark is the end of a "cycle" and you're lo may just need help at night to get through it. Try going in right before the 45 min. mark and laying your hand on him to help him through that jolt.
Sharon