The issue is not the anti-oxidant paste. The spring is made for the greater variation in sizing between an expanded conductor and the size it is when it is not expanded. AL has a greater expansion ratio compared to CU.I have seen the purple wire nuts that are pre pasted and AL rated yet these were very expensive. The paste was alot cheaper to buy and apply myself.
Using regular twist-on connectors and applying the paste is not an approved method of pigtailing.