Yes, you’re right according to a strict application of the physical separation principle. To be clear, the mockup above intentionally pairs a one-way carriageway on one side with a two-way carriageway on the other side. This would require us to pretend that the gore area marked off by chevrons is like a traffic island. That’s what it’s intended to be, but technically you could drive across it without damaging your car, and doing so would be in a legal gray area.
For example, there’s a stop sign poking out of this gore:
To accurately indicate the location of the left turn lane’s physical stop sign or the right turn lane’s stop bar, or the shape of the right turn lane, we do need to relax the physical separation rule for the whole gore, not just the little portion around the stop sign. Tags alone just aren’t very good at encoding geometry. But as I said, there are downsides to this approach, so the dual carriageway I mocked up above should be viewed as a last resort.