"Clathrin-coated vesicles mediate transport between the trans-Golgi network (TGN) and endosomes."
Clathrin coated vesicles: PMID: 12571274
"The coat protein complex I (COPI) allows the precise sorting of lipids and proteins between Golgi cisternae and retrieval from the Golgi to the ER."
COP I vesicles: PMID: 29535154
Our litmus test for additions to cards is "will this additional info be necessary for me to get a question right?"; while this added information is correct, for the purposes of the MCAT, it's beyond what testers would need. So, for the sake of keeping things concise, we'll keep it to the more generalized concept "Vesicles move in retrograde motion."