The same bug that was in java awhile ago where multishot and piercing don't work on pillagers. I am not able to 100 prove this, but from my simple testing they are not able to use the enchantments.
Linked issues
duplicates 1
Comments 2
Thank you for your report!
We're actually already tracking this issue at MCPE-35286, so I will resolve and link this ticket as a duplicate.
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I found this too doing extensive testing I noticed that quick charge doesn't work either. This is very annoying as I was planning on using it for a farm