It's studying or writing (not billable work) that I must do to achieve a good "grade" (i.e., performance review) and it occurs between 9 and 11 pm -- long after

It's studying or writing (not billable work) that I must do to achieve a good "grade" (i.e., performance review) and it occurs between 9 and 11 pm -- long after I've left work for the day. That's the textbook definition of homework. I'm also not the owner or anything of the sort; I'm a mid-level IC with no direct reports.