first of all he said he DID top the plant at 12" thats why he has 2 main stalks that are growing upwards.
in nature plants compete for the sunlight, meaning they grow tall to get the top of the plant to the highest spot above the other plants. this is what happened to your plant. it sensed all the surrounding plants and concentrated on growing tall opposed to building nodes and leaves. this is probally why it is a better indoor strain as they dont have to compete for light. some strains do better outdoors in the woods as they require less light to grow. nutrients may have been a factor but the plant isnt showing much signs of deficiency. maybe try a different strain in thet spot one thats recomended for outdoor growing and stick to your grow room with that strain.
baisicly the rule of thumb is if a plant is stretching it is looking for light, its SoTF. but where MJ is a seasonal plant. it spent too much time seeking out that light to develop those nodes for reproduction.
at least this is my opinion
gl on future outdoors grows