Knockback from the mace smash attack doesn't affect non-mob entities, such as items, wind charges and fireballs. Unsure if this is intentional, but I expected otherwise.
Related issues
Attachments
Comments

[media]
Relates to MC-269377
Can confirm.
Thank you for your report!
However, this issue has been closed as Working as Intended.
If you need help or have a suggestion you might like to follow a link below.
Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki