Generation changes the build step. A team with one of these tools can produce a page, or a new version of a page, by describing it. If building pages was the main obstacle between your team and a better site, that obstacle is smaller now.
The reason for the rest of the cycle is unchanged. You don't know which pages and messages work until buyers respond to them. That is why the method puts a first release in front of buyers and plans to revise it, however the release was built.
Generation also leaves some setup in place. A generator can include forms and other business tools. Someone still has to check that they record what visitors do, and connect the site to any CRM or analytics the company already runs. Those records are one of the main ways a team sees the response to a change, alongside interviews and usability sessions.
A team with steady traffic and someone who reads the results can run this work with a generator and its own tests, without a formal program. Whether to run growth-driven design in-house or hire an agency is a separate question from whether the method still applies.
Checking a change against what visitors did isn't unique to growth-driven design. Other methods do it too. What the growth-driven design cycle adds is a routine for it: a focus metric, a ranked list of changes, a review of the evidence, and a way to pass the lesson on. A generator gives that routine more versions to work with, and the team still has to run it.