JP nope, there is no dust-proof standard. it’s a misrepresentation by the media, especially those on YouTube who parrot words without understanding them.
Essentially, talcum powder is run through a filter screen and particles are made a uniform size and then the enclosure is disassembled after residing in a chamber for a set period of time and it is “visually examined” for dust ingress.
I recently made plaster dust that is smaller diameter than what is tested and it entered my NP3, this it’s not “dust-proof,” nor should it be by IP68 rating (which people continually parrot being dust-proof).
Here’s a screenshot of a test set-up and thus anything smaller than the particle size produced MIGHT enter the phone. I mean 75 microns is huge and dust particles are often smaller.
