The rest of the paragraph you quote is fairly important as it goes on to explain cases and how a project can be cancelled.
The rest of the quote:
In part this is because the approach to this is not uniform across the company. Managers at every level are responsible and accountable for what projects their teams work on, and exercise their discretion as they see fit. In some cases, this means that such decisions are made in a quite bottom-up fashion, with engineers being given freedom to choose which projects to work on, within their team’s scope. In other cases, such decisions are made in a much more top-down fashion, with executives or managers making decisions about which projects will go ahead, which will get additional resources, and which will get cancelled.
The rest of the quote:
In part this is because the approach to this is not uniform across the company. Managers at every level are responsible and accountable for what projects their teams work on, and exercise their discretion as they see fit. In some cases, this means that such decisions are made in a quite bottom-up fashion, with engineers being given freedom to choose which projects to work on, within their team’s scope. In other cases, such decisions are made in a much more top-down fashion, with executives or managers making decisions about which projects will go ahead, which will get additional resources, and which will get cancelled.