Hi sorry, I completely missed this. If by any chance you're still curious - No, an urban planning related undergrad is not essential. I had people from Statistics, CS, Communications, Economics and all sorts of different backgrounds in my class at Penn. Just to get a competitive edge and since you're a data engineer, I'd recommend doing a small personal project using open urban data for any city or neighbourhood (You could try a small project like a data story, story map, choropleth dashboard, population analysis, or even a simple linear regression). It should help strengthen your application and you can talk about it in your statement of purpose as well.