So Physics are immutable, but what the engine understands of your math could be miles away from intended behavior.
A cylinder’s smoothness (or surface normals) plays a role in how an object might bounce off its surface or how a linetrace might check a collision. A cylinder with 6 sides can be told to be smooth, and it will flawlessly be smooth. But a pillar built into some wall geo might warp its smoothness around where it meets the wall (only if it’s part of the same geo, not if it’s two separate objects in the editor). A lot of 3D artists have a hard time with this concept in their first year.