I have read the articles about Canvas' Speedgrader functionality and have seen several places in this community where Speedgrader Student Viewed data indicates this is representative of students viewing instructor feedback.

Here's what the Canvas Docs Include:

I must be missing something.  We see this 'student viewed' date occur in simultaneity with the 'submission' date and time, which can't possibly be reflective of student viewing instructor feedback as it doesn't yet exist.  This happens on some occasions while not in others and I am trying to understand why that is.

Can someone shed light on this---what is the trigger for that data and what is it actually representing within Canvas?

Here's an example of what we see when no annotations are present within DocViewer/Speedgrader (filename blurred intentionally):