You are 100% correct. Just don't use it in any other rifle without full length resizing. The once fired brass in your bolt action should not stretch at all along the case body. What you are doing with neck sizing is just reworking the brass where it contacts the bullet and flows into the free throat of the chamber. You do not touch the shoulder of the case at all and therefore do not shorten the length of the case.
One last word on this. If you take a once fired case from your firearm, neck size it, and put it back into the chamber with your fingers, you should be able to pull it back out, turn it 90 deg., put it back in. Do this for the full rotation of the cartridge. If it is difficult to put back in then the chamber is out of round and you would be better off full length resizing. Your cartridge would be fireformed out of round. You can also tell by rolling the cartridge on a flat surface and looking for a wobble.