Yes, it is indeed built on Unity. I used very nearly the default soft shadow settings - the only changes I made were to decrease the shadow strength to 0.72 so they're a bit more transparent and increase the intensity of the light to 3.2 (my normal mapped materials were rendering darker than I wanted, and in a jam's time constraints it was faster to blow out the light than troubleshoot what was causing this) ;)
It might be because I have a small confined scene with a very shallow depth range, so the shadow map's resolution isn't stretched thin across a huge volume. I also have relatively few curved or thin pointy shapes to reveal jaggies from aliasing, and the camera rarely gets super close to a surface without the depth of field blurring away artifacts that might otherwise be visible.
If you're having trouble in your Unity project, you can often get good advice over at gamedev.stackexchange.com - just be sure to ask a clear and specific question, including a description of what you've tried, examples of the results, and a clear indication of what bits you want to change/improve.