Just because it looks like a reamer doesn't make it a reamer.
It does make holes larger though, and does it in sheetmetal.
Back in ancient times 1950± before plastic grommets in every available size, a tinknocker would first punch a hole with a flatface punch using the end a block of hardwood as a backing die.
From that hole, the tapered tool would be inserted and rotated to enlarge & curb the hole usually over a hole in the benchblock..
That results in something that looks like the male half of an eyelet.
At that point, depending on what the hole was needed for either a ball peen or the tool was used to roll the curb down. The process is similar to double flaring a piece of tubing.