What would stop them changing the policy?
Legally, nothing. They could do that whenever, and they could have already.
I suspect what's stopping them is ethics.
They're having enough trouble retaining staff and dealing with whistleblowers and lawsuits as it is.
How many ex-staff or current staff are suing them, testifying against them in court, or appearing on Channel 4 denouncing them already? With them being possibly one of the more cautious gender clinics in the world?
They're not a private operation cowboy outfit like you see in the US, or GenderGP. They are the National Health Service, getting taxpayer money, and using NHS-trained professionals. It's really not in their culture to just go for "informed parent consent" and wash their hands of the consequences.
We may think GIDS actions have been "surprising" as the judge put it, but as many like Helen Joyce have pointed out, they're one of the best. Because they are the NHS. They're caught at the intersection point between real healthcare and ideological lunacy, and do not appear to have been fully captured by the ideologues.