I think your missing the point, a money drop is about transportation/distribution and not anonymity. Transporting money is the hard part and bitcoin has changes this area more than anything. Being anonymous is easily circumvented by various other techniques, some new, some old.
2018 https://news.ycombinator.com/item?id=18661581
2016 (a bit) https://news.ycombinator.com/item?id=11802353
https://www.damninteresting.com/the-zero-armed-bandit/ - on the same topic - discussed twice in 2015:
https://news.ycombinator.com/item?id=9725851
https://news.ycombinator.com/item?id=9816123