Wither skeletons share the same sounds with skeletons, I consider it important to give them their own sounds for two reasons:
1-Parity with its Java Edition counterpart.
2-If a similar issue with the zoglin was fixed, it should be done with the wither skeletons
Thank you for your report!
However, this issue has been closed.
Going forward we're going to be tracking parity issues not introduced since Buzzy Bees and feature requests on the Minecraft Feedback Site, and we'll be tracking bugs here at bugs.mojang.com.
We're already working on achieving parity across versions where possible, and we're very keen to hear your requests or suggestions, so we'd encourage you to make a post at https://feedback.minecraft.net, or upvote an existing topic there.
If you're not sure whether your issue is a parity request or a bug, hopefully this article will help explain further: Parity Request Guide
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