Already created worlds seem to start by default with fallDamage and doInsomnia on false, while newly created worlds on this snapshot correctly set them to true. In both cases doImmediateRespawn is set to false.
Confirmed to work on multiplayer worlds updated from 19w35a.
Thank you for your report!
We're actually already tracking this issue in MC-160464, 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.
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