Ah, that makes sense!
I was eventually able to make the jump (I think I got a little extra run-up length from a chair), and every time I missed I felt like I was just barely not making it, but using the filing cabinets makes sense. After I got the filing cabinet opening ability, I went and opened every single cabinet, looking for stuff, but didn't find anything - and then I died of the heart attack because I think I missed the rescheduled death contract the first time around. So I filed off opening cabinets in my mind as "only used for getting that one contract" and completely forgot about the ability, haha!