Sad to say, this practice of handing more work to your most efficient worker is common practice, especially if you are on a fixed wage. Corporate will always try to spin it as "We need to know you can handle the workload so we can promote you....blah blah blah"

That's also the reason why so many employees are pushing to WFH so at least when my task on hand is completed, I can go do other non-work tasks and when the workday is over, I can actually relax and do stuff I want to do. Pretty sure Corporate recognise this too and is one of the reasons why they are pushing so hard for people back into the office.