Right, POP control is an option.Or you go pop control Moties.
However under my paradigm, a plateau in POP will also plateau the TL because it will not support the diversity of infrastructure needed at the next TL. Five Thousand People living in paradise with a TL 15 Library Database will never build a Starship from their TL 3 fixed-population community no matter how many generations they work to increase the TL. The Population will never support an Industrial revolution, let alone the infrastructure to manufacture Computers and even an Atlas 1 Rocket.
That was the premise of my [IMTU] link between TL and POP.