Yeah but likely there is a photo period change.
In nor cal and oregon that method will guarantee planting males. This method saves no time or space or resources. And just nice anecdotal story.
In the tropics most modern genetics kinda autoflower so it looks like that articles explanation makes sense.
Ive literally grown many 1000s of seedlings in tropics and many 1000s on west coat 100Ks if count hemp. And no one in the industry uses that to sex plants. Its just an anomaly likely and not saving any time labor etc.
But those acorns the male preflower is never seen until a photoperiod change or in hemp or cannabis with weak genetics in feminized seeds. That female picture is a calyx (?) with out a pistil. The pic below it showing the hairs you can see the calyx open and the two pistils below it. Which you dont get till late july or August during preflower or indoors within the first week 12/12. You will also see the leaflets right at the node below tbe calyx. Many people confuse a leaflet with a calyx. But the sexual structure, be it male acorn or a small calyx with tiny pistils grows from behind or very close to the leaflet. (I use a glass to more easily see when real small, can start sexing many days earlier). This misidentification of a leaflet for a calyx is how sneaky males make it in.
However I have been practicing sexing seeds. Not gauranteed to plant all females but 80-90+ percent females germinated.