Adding to what Sarbar said:

Packaged regular pasta is pretty much a dried paste of flour and water. If you add water, you end up with paste again. Hot water added to uncooked pasta can leave mush, possibly shaped mush, but mush. The water needs to be hot enough long enough to cook the pasta before it starts to dissolve. That is why adding just enough boiling water to reconstitute a food doesn't always cook it. The water temperature cools down too quickly to cook the food.

If the food is cooked and dehydrated, adding hot water brings it back close to the state it was before it was dehydrated.

Does this make sense?

CM