https://developer.roblox.com/en-us/api-reference/enum/CollisionFidelity
Currently the page links to the wikipedia page for “Convex hull” which isn’t the first resource I’d give to developers, but rather some in-engine examples of models affected by it and then later in the page explaining that if developers are interested in more information to go there.
The page notes specifically “The CollisionFidelity property of union objects is not scriptable: it must be set in Studio.” but this should instead just mention the property cannot be set by a script during run time, since geometry cannot be recalculated.
Including some extreme cases where even Default doesn’t work intentionally would also be useful, showing a developer that separating a mesh or making a fake collision (invisible parts) might be ideal right now.
Cases that I think could help a developer understand how it works: