Wither skeleton shoots arrows like a skeleton instead of using sword

I found a wither skeleton in the nether, however, the wither skeleton still shoots arrows and does not use their sword. They have the body of a wither skeleton but are still a skeleton. (I do not know exactly what my tablet is, all I know is that it's a Lenovo tablet, and I am using the full release 0.12.1 of MCPE, there just isn't an option for that).

What I expected: The wither skeleton should walk toward me and try to hit me with his sword.
What happened: It shot arrows at me instead.
How to reproduce:
1. Spawn/find a wither skeleton.
2. Make sure the game is on survival.
3. Get within wither skeleton's view range.
4. Wait to get shot.