In what sense is reserving address space not "preallocating memory"? It might not be allocated to an object, but it certainly is allocated to your process... yes?
No address space does not mean you have memory, you can reserve gigabytes of address space and your process will still show nothing allocated until you commit it.
Ah, of course. Never mind me; when I learned low-level concepts, hardware was much simpler (and so were operating systems).