FWIW…
I ran into this while converting from Concept > Unity/Control Expert. Concept UDTs/blocks “built” the word from internal bits and exposed the word as an output parameter.
I modified the UDT parameter configuration to expose the underlying bits of the word as “public” variables which are picked up nicely by OPC UA Expert via native OFS protocol and exposed as children of the UDT in ignition OPC UA client.
I even removed the word output parameters from the UDTs since they only existed for legacy modbus HMI communication . I also marked the internal/public HMI bits as “Application” tags and configured the PLC/UA Expert to only publish/subscribe to “Application” tags instead of every tag, drastically simplifying the OPC browse tree for clients/Ignition.