^{Update by Bemoty:}
Summary:
When entering a nether portal, there is a very short lag before the loading screen appears.

Steps to Reproduce:

1. Jump into a nether portal in creative mode and keep moving the mouse

Observed Results:
The game lags for a moment before the loading screen appears

Expected Results:
The loading screen appears instantly without lag.

Screenshots/Videos attached: No

Original Description:

When you enter the portal nether the player gets stuck and unable to move for a few seconds