Nether Portal Glitch

When you go through a nether portal in fly mode, you end up at your overworld coordinates, but in the nether. For instance, if you are at 1000 , 1000 in the overworld, then fly through the nether portal using elytra, you will be at 1000,1000 in the nether, you then build a portal, and you are then at 8000,8000 in the overworld