Hi,
I can offer my perspective as a Fiction Reader for a literary journal that uses submittable. I'm a reader, so I'm just giving the first look at a piece and a Yes/No recommendation to the editors. I have a backlog of about 100 submissions, and personally, I too review them in batches when I have a chunk of time. As we get closer to the publication deadline I read more frequently. In-Progress is a good step to be, you're still under consideration! Good luck waiting (the worst part of the publishing process!)