The only "spalted" wood I examined, was some spalted birch and aspen. The discolouring agent appeared to be minerals absorbed into the wood and the wood was not soft at all - as hard as can be and was "finished" into some amazing kitchen cabinets by a local chap, a carpenter/custom cabinet maker friend of Taylor's and mine. He would NEVER use rotting wood for his kitchen cabinets.
I think the term spalted is misused, perhaps in this & Taylor's post or in the posts saying it is the start of rot or is rot.
I have seen a lot of rot in soft woods, conifers and the 'lighter' hardwoods like Aspen and Birch as I was a government tree 'scaler' for a time. I have been initially fooled by what appeared to be spalting/rot in some of these softer hardwoods as in the aspen and birch, but upon further examination, found these to be solid, sound wood, not rot nor approaching rot, simply mineral or mineral/colouring absorbed into the wood by the tree itself.
I have not seen any in maple.