I believe that an old version of Bedrock had sieges. It seems that Java had the same bug but that was fixed.
Comments 5
According to wiki, they were added Pocket Edition Alpha 0.9.0. (I know that it is not an official source for what is intended)
Thank you for your report!
However, this issue has been closed as Invalid.
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.
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I have never seen zombie sieges on bedrock. Seems like they actually never spawn on bedrock like you reported here.