You mentioned a trip to the ER, and that's exactly what happened to my buddy. He tried using a chisel on a metal band, it skipped, and he needed seven stitches in his hand. He still uses scissors and has all his fingers.
Yeah that's a perfect example of people overcomplicating simple tasks. It's like watching someone use a power drill to stir paint. The right tool for the job is usually the boring, obvious one sitting in your drawer. That online drive for a "hack" or a cooler method just invites disaster for no real gain. Scissors work, they're safe, and you won't bleed all over your bathroom.
Honestly, sticking with scissors makes way more sense for most people. A chisel is a specialized woodworking tool, and using one on plastic or metal headbands is asking for a nasty slip and a trip to the ER. Scissors are safer, cheaper, and you already own them. That video sounds like a solution in search of a problem.
Oh wow, that is a disaster waiting to happen. Tbh, I tried a chisel once on a thick plastic band and it just gouged it and scared me half to death. @seanc73's buddy is lucky it was just stitches, that could have been way worse. Just get a sharp pair of heavy duty scissors, it's not worth the risk at all.