Imported part contains blocks

Great, thank you for the explanation!

So when that same part is imported inside of a much larger assembly, Rhino probably reads the tolerances different and that’s why it manages to join more parts and generate less blocks…

(And just to note, both Siemens NX and Unreal Datasmith manages to load this STEP as 1 part with 247 bodies regardless of whether it is in a single part or a larger assembly. To me at least, that’s a more expected behavior, regardless of what is technically correct.)