When holding shift you are unable to fall off blocks which is normal but in 1.15.2 and below when you had levitation you were able to float off them. This has changed in 1.16.2 with this no longer being possible, instead you get stuck on the edge of the block.

To recreate this

1. open 1.16.2 go into a world with cheats enabled.
2. Then find a drop of a few blocks
3. give yourself levitation 255 `effect give @s levitation 10000 255`
4. Hold down shift and try walk off the block.

In 1.15.2 you can walk off the block and stay floating where in 1.16.2 you get stuck and are unable to.