In 2019, Metrolinx included this schematic diagram of the target layout in Union Station rail corridor in a public consultation. It states 30% RCD.
View attachment 451989
Note that the west-facing stub track (13W in the diagram) seems to have moved eastwards so it now overlaps the trainshed, instead of starting at the end of the trainshed and extending out to the Skywalk. Given that there are connections to platforms from Bay St and not from the Skywalk, this looks like a good decision. I looked through the simulation videos but couldn't see any indication of stub-track 13E. Perhaps it's been removed?