Probably an old wives tale, @cogitech. I re-pot in Flowering occasionally and it doesn’t seem to hurt. They usually don’t skip a beat. I do this when I know the plant will turn into a giant, I’ll leave it in a small pot for about 3 weeks. They usually immediately hit a growth spurt for a few days and then stop.
Also, I don’t put them into larger posts until they have 5 nodes. I’ve waited longer some times. It seems that they show within a week of up sizing their pot.
That’s another thing I’ve found in the past. If I have no insect problems, my plants always look awesome after one day in Flowering. If I have a plant that is not looking as good as it should, I put into Flowering early and leave it. I think the plants are getting a photogasm from the 12/12 under the Flowering lamp.
I like that tip, @ReikoX. I’m putting it in to my Grow Journal database so I don’t forget it.
I must be misinterpreting your statement. I find that, on average, the male seedlings present their sex 1st.