In the 2.8.1 version it looks as though not all metadata is correctly exported no matter the settings in the options. I am not talking about the caption etc but all the other IPTC metadata. If I use another application to set this data on import to the ipad - If there is no caption - The copyright already in the photos stays intact. If a caption exists the copyright is stripped. There are also "strange" things happening with exporting images with metadata to camera roll on the ipad.
In previous releases the images exported fine and the metadata was untouched by lightroom mobile. Now it seems the exported data is reliant on there being a title and caption. There are times where i see images with no capture time after export.