Multiplayer/Singleplayer Corruption

Steps to Reproduce:
• Select a multiplayer server
• Before connection to server is complete 'cancel.'
• Join a Single player world.

Description:
• I have no idea what is going on in this video. All I can say is both the single player world data and my server character data is now corrupt.
• My single player character was in creative, still able to fly, but at the same time it seems the internal server thought it was my server character and so I dies to fall damage. This death carried over into the server and had me respawn at my bed. Even better I fell onto invisible blocks that would have been there on the server but not on the single player world.
EDIT: With more testing I can also add that single player character data is carried over to the server. An example of this would be player location and inventory. (I don't think I have to explain why this is bad.)
EDIT 2: I feel it is important to note that the game was switching between night and day because in the single player world it was day and the server it was night.

File size too large here is a download link: https://www.dropbox.com/s/kvevmv388mcdlic/2018-08-03%2001-38-21.flv?dl=0