Sorry to hijack your thread, Donnie! You really are doing a superb job with this build!
I think there were two reasons Mike used the "sistered" frame approach. Harold Hahn was probably the first to use it. First is simplicity. The frames are easy to build. The real Blandford framing was a double frame, followed by two single frames, then another double and two more singles and so on. The double frames themselves started out at the keel looking like a Hahn sistered frame, but the frame then split into two parts, with space between them, almost like a snake's tongue or tuning fork! Very complicated. Also, instead of butt joints, the real Blandford used scarfs and chocks. More complicated still!
The second reason was strength, especially in the single frames. These used chocks and scarfs, with little gluing surface. Unless the chocks fit perfectly, and because of the end grain involved, the single frames could easily break. Using sistered frames throughout made framing much easier and sturdy!