In Minecraft bedrock for smartphones, the Pocket UI profile option comes by default, but I wanted to test the Classic UI profile version out of curiosity (the same version used on the computer) and it was working fine, but when I grabbed an item, I noticed a fluidity that the UI Pocket version was "lacking" in relation to the Classic UI (remembering that both UIs are available in the smartphone's configuration interface), which would be the smoothness of moving items from one slot to another in the Classic UI version.

Note: The video without character/skin is Pocket UI profile and the version showing character/skin is Classic UI profile.

In the video, note that neither has the same fluidity in relation to the two UIs.

Note: Both videos are recorded in the smartphone version, what was changed was just the UI profile in the settings showing that there is an error in the smoothness of Pocket UI as it is not moving items correctly (and smoothly) as they should in the same version Classic UI.