I wouldn't recommend anything to other builders, except to keep an open mind & always try to learn, accepting nothing as solid gospel. If I have learned anything at all from cue making, it's that every time I think I have it figured out, something turns me on my head.
As for cutting fast, I do it. I cut away a lot of wood very fast. I slow things down & make thinner cuts as the shaft is coming close to size. I do it for the very reasons you mention, because I get to find out if they are good or not right away rather than over a several year span. Toss the junk & cut my losses. Not every shaft blank can become a good shaft.
The trouble with this is what I think of as tool induced stress. Basically it's push off from the blade, giving an irregular cut because it's flexing the shaft, and it results in what looks like a warp. Even if you go back & thin cut until it's even & straight again, your center line may still be off, and the shaft will move back to it's happy place again in a short period. Knowing the difference between this phenomena & true internal stress movement is not easy, but makes the difference in the yield if you can learn it. I have found it best to make several thinner cuts rather than one thick cut. It's less stress & flex on the wood, and less strain on the machine & blade. You can still take shafts down fast, just not in a single cut. I have been doing this for a few years & am really happy with my results. Yield seems to be pretty much the same as if I take thin cuts over several years. And to be fair, the time it takes to make a shaft from square or dowel is still about the same. Once I hit 15mm, I slow the cuts way down to a thin cut every few months. The "rush" cuts just helps me identify the bad shafts early. I wouldn't recommend it, though. I like doing things my way, as I feel comfortable, and would encourage others to do the same.
