I started to join a server running 1.14 but cancelled, then opened a 1.14 single player world.

I logged in not at my last coordinates but at the coordinates I was at when I logged out of the server. I logged out of the server in the nether, and logged into my singleplayer world in the overworld, yet I hear Ghasts, and the game is flickering between night and day despite the day/night cycle being disabled.

In addition, I'm walking on air where there were blocks on the server. I also have the status effects that I had on the server, including a beacon effect.

UPDATE: My client appears to have been logged into the server while I was on my singleplayer world, and while moving around, my character was also moving on the server. The ghasts and pigmen I could hear were from the server; as were the status effects.