Hi,
In Moodle 3.7, if the "Marking Workflow" and "Marking allocation" options are enabled, it seems that their respective filters in the "Annotate PDF" tool are not functional, and the number of submissions shown in the tool doesn't change, and it doesn't matter which value is chosen in each of the two filters.
It's so strange, that I wonder if and what I'm missing.
Is it possible that this is a regression bug that was caused because of the fix for the following issue, that was introduced in Moodle 3.7?
MDL-60474 ("Grading interface student switch user tool not reflecting sort order of grading table")