I could go this route, but I was possibly looking for something that wouldn't require me to revisit if we added a category (segment). Otherwise I'd have to create a new calculation every time there are new categories in the data. If I hand this off for someone to maintain, I wouldn't want to have to update it every time for this calculation. I hope that makes sense.
Sidenote: my example has 3 categories, but our actual production data has at least 15 categories.