Issue in action: https://gfycat.com/nervouspreciousirishterrier

In 1.12.2, teleportation would move the player but not restrict their movement, meaning they would experience no loss in momentum or difficulty in moving, falling, etc. You can see in the gif how I have no restrictions in my movement and can run and jump just fine, though I am being pushed in one direction. This was great, as it allowed for a lot of possibilities with minute teleportation.

In the latest 1.13 snapshot (17w46a as of posting), teleportation works completely differently. Instead of moving the player slightly, each teleportation freezes them in place (seems to me like for the remainder of the tick). This makes it feel like your legs are trapped in mud and you have to struggle for every inch, rather than the smooth feeling of as if you were in a strong breeze pushing you in one direction. In the gif, you can see how I can barely move my camera angle, can move my player even less (it's no longer possible to move against the small teleportation, only slide very slowly to the sides), and cannot jump at all. Creative mode did allow me to start flying, but when I stopped flight I didn't even fall downwards!

If you would like to feel the effects yourself, you can type in the commands seen in the gif in their respective versions. Please note that due to the difficulty in moving with the 17w46a teleportation you will most likely be unable to reach the command block after too long, so be careful and make sure you can get rid of it or turn it off from afar.

Testing by running small teleportation commands 20 times a second on villagers revealed the following:

• If you are being constantly teleported in any direction, you will not fall.

• When teleporting an entity to relative coordinates (~, ~, ~), which does not change their location AT ALL, the entity/player is still frozen in place, unable to move, look around, or fall.

• When teleporting an entity, they gain high (though not total) knockback resistance, as they are able to move a lot less.