The whole spine / not spinning always is a back & forth thing among rod builders. Most builders when they first start out will find the spine, then as they build more and more rods they drift to simply building on the straightest axis. The spine of a rod is very easily overcome with any amount of pressure and really has nothing to do with power or breakage at all. Over the years myself as well as many other builders have built two identical rods (one with guide on spine and one on straightest axis) and found zero difference in casting or feel. The only time spine "might" make any difference is in something such as a deep sea rod like a tuna rod where you have a tremendously stiff rod blank then there is a chance it'd come into play, but for anything else the spine of a rod does not affect strength, casting, or breakage and is nothing more than just something some companies/builders like to throw around to make building seem even more like black magic.
The whole spin/spline thing really started years ago back in the 70's/80's with Dale Clemens rod building book. That's when many people read what he said and took it as truth. Thing is that was 40 yrs ago, the process and materials for building blanks and the scrim and such has advanced hugely since that book and a lot of things are no longer true, if they even were at the time it was written. There are some that will disagree with me, but that's been going on for years with those that like to spine so nothing new there