you control flowering is based on the size plant you can have at harvest. If you can only have a 2ft plant then you flower directly from seed.
If you can have a 10ft plant flower when the plant is 3ft.
Typically everyone is indoors and have a 8ft ceiling subtract a couple feet to keep from burning plants from the light. Subtract the height of a large pot. Now you have a space of 5ft tall.
Plants double or triple when they flower.
So you could go as high as 2ft in veg. but the added time to get 2ft isn't directly proportional getting that much now product. They have found you and turn out more little plants and get an ok yield than growing large plants for a longer time and get a big yield.

You say you have 4.5ft, just flower 12" and call it good.