I am in flower on two of three seed plants(one hermi'd), as a trial learning grow. I'd wondered the exact same thing.

However, I found that if the branch has enough light, it almost never does. Of the three plants I grew. One was natural, One was topped, and one I LST'd.

Once the plant had branches where the light BARELY got to them. Those branches started to stretch to try and get more light. THESE switched to single leaf nodes until they got more light.

ALSO, branches OFF of branches grew as singles.

Hope that helps.