Wither skeletons with bow still shoots fire arrows

Despite tipped arrows are added in game, the wither skeletons with bow still shoots flame arrows, instead of tipped arrows.

What I expected to happen:

The wither skeleton shoots arrow of delay.

What actually happened:

The wither skeleton shoots flame arrow.

Steps to Reproduce:

1. /summon minecraft:wither_skeleton ~ ~ ~ {HandItems:[ {id:bow,Count:1b}

   ]}.

1. Let's it to attacking someone.

It shoots flame arrows.