When creating a new image UISO set by default (at least in my PC) CD/DVD Data mode. If the file is bigger than 4GB it alerts and ask if you want to change to UDF DVD.
If you say yes the settings are changed to UDF DVD but differ from those set when you chose File->New->UDF DVD project.
It's not a bug, it's an inconsistency. It should set the same parameters when switching to UDF as if an UDF DVD was selected from the File->New->UDF DVD menu.