In the Java edition of Minecraft, consider the following key sequence:

[press E]
[start holding W, A, S, or D]
[press E]

This will cause the player to immediately start moving upon closing their inventory. This behavior is not replicated in the Windows 10 Edition. It should also be noted that this key sequence returns a similar effect:

[press E]
[press E]
[within ~0.2 seconds of the previous key press, start holding W, A, S, D]

Its hard to know for sure whether this is intended behavior, but I assume it is a bug for the following reason:

When playing multiplayer games, especially within combat, it is extremely important that the transition from inventory to movement is fluid. The current behavior is both confusing and limiting.