Virtual memory (memory paging and segmentation) is the foundation for being able to start and stop apps. Otherwise memory would have to be defragmented. Both don't require the ability to store somewhere, they both are useful in physical memory only situations.
I think what he means in the article is that Apple disabled Mach's ability to store memory pages on disk in order to free room for more physical memory. The most probable reason being that Apple does not trust the lifetime write capacity of their Flash disk. (And depending on your chicken and egg, the current App situation does not require swapping memory pages to disk since you can only run one App at a time. Which caused the other I don't know.)
