I don’t think this is the best forum for this question — better to try another one on the Internet, such as through Reddit.
This question, even there, is very difficult to answer. It is believed that it can take some time for certain exfoliants, including retinoids, to help blemishes emerge (purge). In other words, for certain people, their skin might look worse for a while before it gets better. How long does this process take? In theory, it could be up to 30 days. So for certain, if a product is clearly worsening one’s acne beyond 30d, the product is causing breakouts — not purging.
But obviously it is possible that some one could use a product for even a single day and break out from it. There are people who might label that as “purging,” but you cannot really say for sure unless you give it time.
Note that this only applies to exfoliants: AHA/BHA/retinoids. I have never heard of a single dermatologist saying that a moisturizer, for example, *without* an exfoliant could cause purging.