Sorry I would love this to be true but this is just PR bollocks isn’t it?
The claim: “Millions of workers will have a say over their working patterns”.
The reality: “If a worker’s existing working pattern […], they will be able to make a formal application to change their working pattern […]. Once a worker has made their request, their employer will be required to notify them of their decision within one month.”.
So you have the right to ask (as if you didn’t already), and your employer has to respond within a month (but they can still just say “no”). What am I missing here?

So like, this just means that a worker can ask, not that the employer has any reason to grant that request?