your arm doesn't swing enough across your chest like in java addition. It barely goes across your body. This effects 1.5.0.1

How to reproduce

1. Load up a superflat world on Minecraft Java Addition and Minecraft
2. On minecraft java addition enter in chat /effect give @s mining_fatigue 30 15 true
3. On Minecraft enter in chat /effect @s mining_fatigue 30 15 true
4. Go into third person view (front) by pressing LT twice or by pressing F5 twice
Steps 3 and 4 will slower your arm swing speed
5. Compare the length the arm swings across your chest for both versions.