Hi Clive,
There are two things that make interpreting the shoulder motion of pros tricky:
1 - We don't have any good data sets of direct measurement (measuring the scapula and sc joint are hard to do)
2 - Since there are lots of motion options at the shoulder, there are probably different patterns.
To answer your question, On 3D, we do see the lead shoulder typically raise compared to the thorax. That likely is a sign of the lower body leading the downswing and the spine going into flexion while the arm "stays up", and it also compliments lead arm internal rotation (which I haven't seen data on but still support as a shallowing movement).
The trail shoulder appears to go into external rotation, so typically, the trail shoulder blade would compliment that movement and go into some depression and downward rotation. Perhaps this video helps that concept https://www.golfsmartacademy.com/golf-instruction/shoulder-blade-shallowing/
Let me know if that helps clear it up,
Tyler