Thanks for sharing! Good to hear others trying this too.
I recently tried the quartering method to jumpstart my sugarloaf patch, and am in the middle of it. Since they were shipped with crowns cut down I tried the route of a light rooting in water first just to test viability. I am in Arizona so plants are indoors on a window sill for now.
July 14th: Placed crowns in water with little rooting hormone.
July 24th: Roots got 1/2 to 1 inch long, quartered the crowns, planted in off the shelf potting mix + perlite. 16 total. (Hindsight should have throw in peatmoss)
August ~7th: lost one to rot. Turned black and moldy. Realized I cannot provide water on the cut side in my environment (low airflow). I now water lightly every 3-4 days on just the not-cut side of the crown now. Also note water rooting may have compounded.
August 30th: 4 of them have visible new growth now, the other 11 still alive waiting to pop.
Comparing your timelines to mine, looks like simply cutting and planting is the way to go. I gained nothing by trying to root in water first other than assurance the crowns were still viable.
Will move to peat moss/acid based soil outdoors as they start showing growth.
Happy growing!
Also, after reviewing the image of the roots when I quartered them, I'd be tempted to even try cutting into 1/6ths or 1/8ths.