Good article, but I feel that it misses an important property of diffusion models that they model the score function (derivative of log prob) [1] and that diffusion sampling is akin to Langevin dynamics [2]. IMO these explain why it's easier to train these models than GANs, because of an easier modeling objective.
The difference is that Apple/Google contact tracing gives the user control over their data. Singapore's app works differently. Once someone's app picks up your signal, it's logged on their device and there's no way to delete it. The data is handed over to the authorities who have a list of everyone that they interacted with. Source: https://www.straitstimes.com/singapore/apple-google-contact-...
[1] https://yang-song.net/blog/2021/score/
[2] https://lilianweng.github.io/posts/2021-07-11-diffusion-mode...