Yes, the article is accurate and it shows you not only what is theoretically possible but even practical to do. However, for something to be practical, even when all the assumptions are met, doesn't imply that it is cost-free. The idea of participating in a multi-party transaction (aka coinjoin) is to create, in the worst case, an imbalance where it is cheap for you to gain privacy while it is costly for an attacker to try to deanonymize you. We can see this cost in the real world where huge bounties are offered to track some entities which paid cents for joining a crowd in a coinjoin.