Seedlings take a lot longer vegging time before they are ready to switch no matter what size the yield you are after. Sometimes seedling do not display all their adult parts until between 2-4 months from popping. Without all the adults bits in play they will stress badly if put into flowering too early. This is something I see quite commonly with indoor growers these days. Even the standard belief that clones are ready to bud in 3 weeks is often wrong. Seedlings need to be given time like clones in order for the roots to fill out the grow medium in your pots. They also need time to adjust to being fed nutrients, a sign of that is increased nutrients does not lead to nutrient lead burn.
They also need time to allow their metabolism to begin to increase, a sign of that is increased need to water them. Also the walls in the stems need time to thicken and the plants gender needs time to show. The gender bit often gets brushed over these days with most growers opting for feminized seeds. Feminized seeds need more than standard seeds, time to form their adult parts as they often can carry a hermaphrodite gene from one of their parents. The greater chance they have to develop all their adult structures that better chance they will have against stress.
Other signs that your plants are ready to bud are that they fill out the pot they are in. This is a sign that the roots are filling out the pot below them. Leaves extend outward pretty much at the same rate as roots extend out. Leaves that struggle to extend out like those in the pics, are a sign that there is something going wrong in the root area. My guess is that the roots have not formed properly, 'possibly' from incorrect watering. The affects of that would be stunted growth, leaf tips easily burnt and leaves staying short and bunched rather than stretching out.
I just popped into my tent and shot that pic, that blueberry is in a 50 litre. It came from a clone but I still left it to veg for 5 weeks due to the fact it had spider mite when I got it. After ridding it of the infestation it took another 2 weeks to perk up and begin growing again and the leaves only reached the sides of the pot just under a week ago.
It is only just starting to use up nutrient at a faster rate, and my increased feeding is not resulting in leaf problems. These are the signs we need to look for before switching a plant to flowering to give them the best chance of handling that period of their growth.
It will get another week in veg before I am happy to switch it. Anyways the point of this is that our eyes are the best guide to tell when a plant is ready to switch rather than abitrary times or measuring plant height or even the yea old counting the nodes trick.
Sorry I cannot be of more assistance to you.