disclaimer: my opinion throughout, I'm not a pro 3D modeler.
https://i.imgur.com/2RmKuAo.jpg
This is PlanCo's Half Prolate Spheroid 5 - Extra Large, base upward. It has 20 edges around the base, which is sharp -- the rest of it's pretty smooth, despite being low-poly. So it looks like PlanCo is using smooth shading, with some way of exempting what needs a sharp crease -- pretty standard for 3D games and programs.
In Blender (and similarly in many 3D programs and game engines) there are two main ways to do this -- I made a spheroid to demonstrate:
https://i.imgur.com/OV78OhY.jpg
Mine has 130 polygons (all quads, so 260 in-game tris), and (like PlanCo's) 20 edges around the base. If I select the base edges and have Blender "Mark Sharp" then my spheroid's smooth-shaded except around the base, which has a nice sharp crease. But would it import that way into PlanCo?
The other way is to run a couple edge-loops around the base, close to where it should crease sharply (aka "proximity loops", "holding loops", etc):
https://i.imgur.com/4WVwxDT.jpg
This is more likely to import prettily regardless, but it ups the polygon count (adds 40 quads here, so 80 tris in-game), which burns more resources when it's used in the game -- as a general rule, anytime you can get what you're going for with fewer polys, you should. Which brings up the question: will we be able to import models with some form of "Mark Sharp" in them?
For those trying to get importable stuff ready for whenever the Thememaker's Toolkit goes live, this is a question it'd be really helpful to have answered ASAP . . .