I've rebuilt the whole woodland mansion and placed in some waterlogged blocks too, I've applied the structures with a datapack, and when the server generates the building, it waterlogs the sorrounding waterlogable, not waterlogged blocks. I've experienced it in 1.13.2 as well.
This is the original structure:
[media]And this is the generated part:
[media]
Thank you for your report!
We're actually already tracking this issue in MC-127644, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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