My guess is that bushy plants with lots of heads stretch less because energy is distributed between many smaller sites as apposed to if was just 1 single stalk sucking up all the stretching power. Also with good strong lghting you get less stretch. And one last thought, the more mature a plant is, like your bushy beasts, compared to a smaller less heads younger single stalk plant, the more mature plant can take longer to initiate flower but in the end outperform the younger plant. And another thing, lol, when you want to initiate flower response quickly in the plants, drop any nitrogen source and up the P and the K in the mix to higher than usual levels for those first few days and this will induce strong flowering response. Complete balanced main Bloom fertilizer is not what I mean here, I mean a product like Rambridge Blossom Blood, Advanced Nutrients Bud Blood, Grotek Blossom Blaster, at 0-39-25 ratio, even a regular bloom booster like somethng with a 0-50-30, you cut out the N compoletely for first few days and feed high P and K and plants will flower very quickly then on to your regular complete balanced bloom feed. old old trick
When initiating flower, the plants should be healthy not yellow or any deficiency, this way the super low or zero Nitrogen added just for a couple days will not fuck them up.
Drop the N completely, give your bloom booster to trigger them
in good bloom products that contain amino acids and have no N value, the amino acids are the building blocks of life and will sustain them and keepo metabolic Nitrogen processes and green leaves going, brother.