Ah yeah, I remember that. I converted my 10x135mm Hope hub back in the day to 12x142mm and it snapped. Replaced it and it snapped again. Hope then shipped me a steel axle for free and it was fine after that.The hollow axle is completely unsupported in the centre. With a 12mm TA that's generally the same internal width of the axle isn't it? I think some older Hope axles had issues because the external machining design left too much of a stress riser, so they altered it to be a more gradual angle...
The first time it happened I didn't even know that it had snapped, until I took the rear wheel off for some maintenance and the entire cassette/freehub fell off onto the ground. Oops.