Astronomers may have found giant alien 'megastructures' orbiting star near the Milky

[stevebowers]

Taking this to a more general case, it is generally agreed upon that any long lived culture is going to have to control it's population eventually or suffer collapse. So why would it not institute such a thing before a dyson is built instead of after? Especially when related tech (longevity) would seem to make the need even more urgent, and the solution (perfect and easy birth control) even more easy.

Putting this all together an advanced civ might have the means to create a dyson, but deliberately limit its population where such is not required even though the population is vastly larger than what we have now.

Exactly. I have already (before I read your comment) put a message to this effect on the comments section of that article.

I think the idea is that 'any advanced civilisation is compelled to make maximum utility of all its resources in as short a time as possible'. Many futurists think that the function of superintelligence is to increase the evolutionary fitness of the entity or entities concerned, making every action part of a struggle to maximise their control over the environment. Anders may be thinking along those lines; what is better than half-a-Dyson? A whole Dyson, of course.
But once you reach the limits of growth you are forced to scale back your expansion anyway; why not do it before you reach that stage, while you still have a choice?