yes this is a difference concept, but as you’ve noticed the word in programming is used for something not quite the same and could be confusing that’s correct.
though actually is not very different, just that this is an instance from the pov of the gpu so it’s rooted on 3d concepts and not programming concepts. afaik is called similarly on different engines. (in defense of epic). i guess it never occurred to me since i already knew the concept from other engines.
the gpu mostly cares about the transform (and maybe materials).
though these are “static mesh instances” (which means instance of static meshes), and not actor instances. so maybe that also helps remembering the difference.
for example godot also call them “instances” Godot Engine Nodes - MultiMeshInstance2D - YouTube
though godot has many similarities to ue (take with a grain of salt they’re 2 different beasts).