This is not true at all. If this was true then mites wouldn't be nearly as much of a problem as they are. Mite eggs do not necessarily hatch right away. They can linger for several weeks and wait for better conditions before hatching. This is a well documented fact. I used to have issues with mites on a regular basis until I finally got them out of my grow and took drastic steps to avoid recontamination. At one point I got rid of the mites in my grow, but I continued to use the same bamboo stakes that I had used previously and sure enough I got them again. Fortunately, the mites only appeared on a single branch that was directly tied to the bamboo stake. I noticed it right away, cut off the branch and didn't see anything else. I considered myself very lucky. They must have stayed confined to that branch since there weren't that many of them yet. The bamboo stakes had been in my back yard baking in the sun for at least a couple of weeks before I took them back into the garage. I sprayed them off with the hose at one point, but that was it. The stakes were not near any other foliage and it's very unlikely that they were contaminated while they were outside. Who knows, it could have been a single egg that hitchhiked in a crevice of the bamboo stake.
Mites are the absolute WORST thing that can happen to a cannabis plant. I haven't had any in a couple of years now and I'm terrified of getting them again. I rarely bring outside clones/plants into my grow and if I do I quarantine them for 30 days before letting them socialize with any other plants that I have.