Hi Jeremy,
Dynamo has its own geometry engine, allowing it to perform more types of geometric operations than Revit can do.
E.g. there are more possible ways of object intersection.
As far as I can see, Dynamo can calculate geometry from input data and create/show the result in Revit as static Elements, either as ImportInstance (e.g. SAT file) or DirectShape; in this case, Revit is just the display.
But the calculation itself is being done inside Dynamo, using its own engine.
So if there is a performance issue, it may be found there, inside Dynamo.
Rudi