That's correct. A reservation does not get created into anything. The reservation is ademand for material. The reservation is used by the MRP run. MRP will take all of the the reservations into account and create a PR for you. The whole point of using plant stock is to collect all of the requirements together and buy in bulk. To do this you wil need to execute MRP.
If you just want a PR for your project then use project stock and have the network activity create a PR directly.
