To the contrary, there are multiple methods of early detection. One of which Misc M.O. you take a light adhesive tape and some dark paper and the idea is that you want to cover a section of a single branch at the same time every day acting as "light deprivation" to that one location. As normal, within a week or more the parts that you are concerned about will have accentuated and revealed themselves. That's one. It's labor intensive but if you want it- it works.
Second, and some say that it's pseudo-science and horse shit but I've been doing it with a high percentage of success for years so it's note-worthy. You're going to want to have a jeweler's loupe handy. Preferably 30X or greater or a dual loupe with 30X and 60X both. The part that people say is horse shit: When looking at a seed bottom, and by bottom I am referring to the part of the seed that attaches to the placenta within the bud, you will see:
A) A perfect volcano
B) A collapsed volcano
C) A nub, or "outie" so to speak
These are three most common but if you've been stairing at the ass-end of seeds under a magnifier long enough there are actually several more variations. In general, a "perfect volcano" is a female seed. Now, this has been disputed so many times over and with complete disregard to other factors involved. Namely, when you look closely at the side of a cannabis seed one notices the presence of stripes or splotches, spots etc. These mean absolutely nothing in relation to sex, however, and feel free to dispute me on this until you've tried it yourselves because practically no-one has;
A female seed can just as well have an "outie" and what is in question here is IF the outie can easily be removed(placental attachment) leaving a perfect volcano behind. Male seeds simply will NOT have a perfect volcano. there will be a collapse or a partial volcano; But the placenta fully detaches from female seeds whereas male seeds exit taking part of the placenta with it. Hermies; Look for a collapse or a partial collapse on the attachment end THEN turn the seed over and look at the sharp end. The sharp end on a hermaphrodite will have what appears to be a small "cleft" at the end. Straight-sexed seeds(ie: XYX, YXY) will come to a sharp point. Depending on lineage the point side of the seed can either come to a perfect point or will be rounded but will NOT display a cleft, a split, or a second volcano.
Hermie's(ie: XXY, YYX, XYY, etc) point side of the seed will display a cleft, a split or a second smaller volcano.
Another factor in "seed sexing" that needs be taken into account and applied is IF:
A) The seed is dominantly round and capable of rolling when gently flicked with a finger on a smooth flat surface
B) The seed is oblong and slender and tumbles when flicked
C) The seed is uneven and fatter on one end than the other or is proportionately unbalanced
There are always exceptions to the rule here.
I mean, if a seed has a perfect volcano on one end and comes to a point on the other yet is oblong and slender and doesn't roll, you have a Y dominant hermaphrodite seed.
If you have a seed with a perfect volcano at one end and a smaller volcano on the other end you have a feminized seed.
If you have a perfectly round volcano on one end and she comes to a point on the other and if she rolls across the table that baby is XYX, you have a girl, start getting busy!
If you have a partial volcano or a collapse on one end and a sharp point on the other you have a male.
If you have a partial volcano or a collapse on one end and a split or a cleft you have an Y dominant hermie.
If you have a perfect volcano on one end and a split or cleft on the other you have an X dominant hermie.
Again, there are so many identifying combinations that make up female and male seeds that one cannot use the volcano spotting method alone. You have to look at both sides of the seed and whether it's flat or round and there are any number of combinations in between. I could bore you with them but you already get the idea.
You can go on ahead and tell me I am full of shit but the last time I picked a male seed by accident was 2015.