Because they are not in the current Mitsubishi Diamana production line and wouldn't be stocked. Diamana new shafts are "X-Series, +PLUS, RF/BF/DF/ZF, Thump". Check the Mitsubishi website for details.

In testing, Titleist matches shafts to new head designs. They then have a "stock" matrix of shafts for retailers to display on the rack, but any shaft in the custom catalog can be ordered.

The Daimana LTD D+ 70 or 80 White is in the custom options list as a n/c upgrade and is the successor to the white board. If your fitter doesn't have that shaft for fittings, the local rep can work to loan one for a scheduled fitting. But let the fitter help you decide which shaft to use.

You can still get them, no upcharge, most shops will let you demo them if they have previous 917 models still. I got the diamana 'ahina in my ts3.