It's an engine written in C++ (not Unreal) that we've added C# scripting to. So it's in the same kind of situation as Unity where their engine calls from C# lan

It's an engine written in C++ (not Unreal) that we've added C# scripting to. So it's in the same kind of situation as Unity where their engine calls from C# land need to be marshaled into calls to native code and back, which of course has overhead.