A user on Discord pointed out that if you fly through a nether portal with a speed of 5 (I used EssentialsX to set the speed), it will take you to that world's respective end world. Upon further inspection, it seems when flying quickly (in this case, a speed of 5), MV NetherPortals fails to detect that the portal is a nether portal and is instead treated as an end portal due to the implementation of our PlayerPortalEvent listener.